搜尋
首頁資料庫mysql教程Python中使用SQLAlchemy连接Mysql数据库(单表操作)

一,SQLAlchemy的安装 使用 $ easy_install sqlalchemy或 $ pip install sqlalchemy 如果出现什么错,就进去root用户下进行安装试试,或者网上查查 import sqlalchemy 这样说明成功了,切记是小写哦 二,使用 理论我也不懂,自己查查资料,现在用一个小的案

一,SQLAlchemy的安装
使用

<code class=" hljs ruby"><span class="hljs-variable">$ </span>easy_install sqlalchemy
或
<span class="hljs-variable">$ </span>pip install sqlalchemy</code>

如果出现什么错,就进去root用户下进行安装试试,或者网上查查

<code class=" hljs python"><span class="hljs-prompt">>>> </span><span class="hljs-keyword">import</span> sqlalchemy
<span class="hljs-prompt">>>> </span></code>

这样说明成功了,切记是小写哦
二,使用
理论我也不懂,自己查查资料,现在用一个小的案例说一下使用步骤
1,在进行数据操作之前要先连上数据库。

<code class=" hljs python"><span class="hljs-prompt">>>> </span><span class="hljs-keyword">from</span> sqlalchemy <span class="hljs-keyword">import</span> create_engine
<span class="hljs-prompt">>>> </span><span class="hljs-keyword">from</span> sqlalchemy.orm <span class="hljs-keyword">import</span> sessionmaker  
<span class="hljs-prompt">>>> </span>DB_CONNECT = <span class="hljs-string">'mysql+mysqldb://root:102@localhost/mydb'</span>
<span class="hljs-prompt">>>> </span>engine = create_engine(DB_CONNECT, echo=<span class="hljs-keyword">True</span>)
<span class="hljs-prompt">>>> </span>DB_Session = sessionmaker(bind=engine)
<span class="hljs-prompt">>>> </span>session = DB_Session()
</code>

from 是从sqlalchemy中插入必须的模板,DB_CONNECT 是构造数据库的路径 ,mysql+mysqldb是说明使用MySQL-Python 来连接,root是数据库用户名,102是密码,localhost表示是数据库在本机上,mydb是要连接的数据库名字,设置字符集的charset可以省了
create_engine() 会返回一个数据库引擎,echo 参数为 True 时,会显示每条执行的 SQL 语句,生产环境下可关闭。
sessionmaker(bind=engine)会生成一个数据库会话类。这个类的实例可以当成一个数据库连接,它同时还记录了一些查询的数据,并决定什么时候执行 SQL 语句。由于 SQLAlchemy 自己维护了一个数据库连接池(默认 5 个连接),也可以自己设置。
得到session 后,就可以执行 SQL 了:
2,在进行操作前先把表给建立了,由于SQLAlchemy 可以和变进行建立连接并且可以通过语言进行见表

<code class=" hljs avrasm">mysql> show tables<span class="hljs-comment">;</span>
Empty <span class="hljs-keyword">set</span> (<span class="hljs-number">0.00</span> <span class="hljs-keyword">sec</span>)
mysql> </code>

此时是没有表的,现在我们建立一个学生便stu,一个课程表cla和一个成绩表grade

<code class=" hljs r">>>> from sqlalchemy import Column
>>> from sqlalchemy.types import CHAR, Integer, String
>>> from sqlalchemy.ext.declarative import declarative_base
>>> from random import randint
>>> from sqlalchemy import ForeignKey
>>> BaseModel = declarative_base()
>>> def init_db():
<span class="hljs-keyword">...</span>     BaseModel.metadata.create_all(engine)
<span class="hljs-keyword">...</span> 
>>> def drop_db():
<span class="hljs-keyword">...</span>     BaseModel.metadata.drop_all()
<span class="hljs-keyword">...</span> 
>>> class Stu(BaseModel):
<span class="hljs-keyword">...</span>     __tablename__=<span class="hljs-string">'stu'</span>
<span class="hljs-keyword">...</span>     id = Column(Integer,primary_key = True)
<span class="hljs-keyword">...</span>     name = Column(CHAR(<span class="hljs-number">30</span>))
<span class="hljs-keyword">...</span> 
>>> class Cla(BaseModel):
<span class="hljs-keyword">...</span>     __tablename__=<span class="hljs-string">'cla'</span>
<span class="hljs-keyword">...</span>     id = Column(Integer,primary_key = True)设置主键
<span class="hljs-keyword">...</span>     cname = Column(CHAR(<span class="hljs-number">30</span>))
<span class="hljs-keyword">...</span> 
>>> class Grade(BaseModel):
<span class="hljs-keyword">...</span>     __tablename__ = <span class="hljs-string">'grade'</span>
<span class="hljs-keyword">...</span>     uid = Column(Integer,ForeignKey(<span class="hljs-string">'stu.id'</span>))设置外键
<span class="hljs-keyword">...</span>     cid = Column(Integer,ForeignKey(<span class="hljs-string">'cla.id'</span>))
<span class="hljs-keyword">...</span>     id = Column(Integer,primary_key=True)
<span class="hljs-keyword">...</span>     gre=Column(Integer)
<span class="hljs-keyword">...</span> </code>

declarative_base() 创建了一个 BaseModel 类,这个类的子类可以自动与一个表关联。以 Stu 类为例,它的 tablename 属性就是数据库中该表的名称,它有 id 和 name 这两个字段,分别为整型和 30 个定长字符。Column 还有一些其他的参数,我就不解释了。
最后,BaseModel.metadata.create_all(engine) 会找到 BaseModel 的所有子类,并在数据库中建立这些表;drop_all() 则是删除这些表。
现在执行init_db()进行建立表,对应语句如下

<code class=" hljs vbnet">>>> init_db()
CREATE TABLE stu (
    id <span class="hljs-built_in">INTEGER</span> <span class="hljs-keyword">NOT</span> NULL AUTO_INCREMENT, 
    name <span class="hljs-built_in">CHAR</span>(<span class="hljs-number">30</span>), 
    PRIMARY <span class="hljs-keyword">KEY</span> (id)
)

CREATE TABLE cla (
    id <span class="hljs-built_in">INTEGER</span> <span class="hljs-keyword">NOT</span> NULL AUTO_INCREMENT, 
    cname <span class="hljs-built_in">CHAR</span>(<span class="hljs-number">30</span>), 
    PRIMARY <span class="hljs-keyword">KEY</span> (id)
)
CREATE TABLE grade (
    id <span class="hljs-built_in">INTEGER</span> <span class="hljs-keyword">NOT</span> NULL AUTO_INCREMENT, 
    uid <span class="hljs-built_in">INTEGER</span>, 
    cid <span class="hljs-built_in">INTEGER</span>, 
    gre <span class="hljs-built_in">INTEGER</span>, 
    PRIMARY <span class="hljs-keyword">KEY</span> (id), 
    FOREIGN <span class="hljs-keyword">KEY</span>(uid) REFERENCES stu (id), 
    FOREIGN <span class="hljs-keyword">KEY</span>(cid) REFERENCES cla (id)
)
COMMIT
>>> </code>

以上就是执行时对应的建表语句,现在去数据库看看表是否存在,并查看一个表结构

<code class=" hljs asciidoc"><span class="hljs-header">mysql> show tables;
+----------------+</span>
<span class="hljs-header">| Tables_in_mydb |
+----------------+</span>
| cla            |
| grade          |
<span class="hljs-header">| stu            |
+----------------+</span>
3 rows in set (0.00 sec)
</code>

表已经建立成功了,现在看一下表结构

<code class=" hljs asciidoc"><span class="hljs-header">mysql> desc grade;
+-------+---------+------+-----+---------+----------------+</span>
<span class="hljs-header">| Field | Type    | Null | Key | Default | Extra          |
+-------+---------+------+-----+---------+----------------+</span>
| id    | int(11) | NO   | PRI | NULL    | auto<span class="hljs-emphasis">_increment |
| uid   | int(11) | YES  | MUL | NULL    |                |
| cid   | int(11) | YES  | MUL | NULL    |                |
| gre   | int(11) | YES  |     | NULL    |                |
+-------+---------+------+-----+---------+----------------+
4 rows in set (0.00 sec)</span></code>

可以看出 使用SQLAlchemy中的语句和使用SQL语句的结果一样。接下来就可以插入数据了

<code class=" hljs python"><span class="hljs-prompt">>>> </span>stu = Stu(name=<span class="hljs-string">'a'</span>)
<span class="hljs-prompt">>>> </span>session.add(stu)
<span class="hljs-prompt">>>> </span>stu = Stu(name=<span class="hljs-string">'b'</span>)
<span class="hljs-prompt">>>> </span>session.add(stu)
<span class="hljs-prompt">>>> </span>stu = Stu(name=<span class="hljs-string">'c'</span>)
<span class="hljs-prompt">>>> </span>session.add(stu)
<span class="hljs-prompt">>>> </span>stu = Stu(name=<span class="hljs-string">'d'</span>)
<span class="hljs-prompt">>>> </span>session.add(stu)
<span class="hljs-prompt">>>> </span>stu = Stu(name=<span class="hljs-string">'e'</span>)
<span class="hljs-prompt">>>> </span>session.add(stu)
<span class="hljs-prompt">>>> </span>
</code>

手动插入了五条记录,但此时还没有提交,没有真正的写入数据库
或者使用非ORM方式进行插入

<code class=" hljs ruby">>>>session.execute(<span class="hljs-constant">Stu</span>.__table_<span class="hljs-number">_</span>.insert(),[{<span class="hljs-string">'name'</span><span class="hljs-symbol">:randint</span>(<span class="hljs-number">1</span>,<span class="hljs-number">100</span>)} <span class="hljs-keyword">for</span> i <span class="hljs-keyword">in</span> xrange(<span class="hljs-number">10000</span>)])
>>>session.commit()
<span class="hljs-comment">#可以速度更快的插入更多的数据</span></code>
<code class=" hljs avrasm">>>> session<span class="hljs-preprocessor">.commit</span>()
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">839</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> BEGIN (implicit)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">840</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> INSERT INTO stu (name) VALUES (%s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">840</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'a'</span>,)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">841</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> INSERT INTO stu (name) VALUES (%s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">841</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'b'</span>,)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">841</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> INSERT INTO stu (name) VALUES (%s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">841</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'c'</span>,)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">842</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> INSERT INTO stu (name) VALUES (%s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">842</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'d'</span>,)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">842</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> INSERT INTO stu (name) VALUES (%s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">842</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'e'</span>,)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">22</span>:<span class="hljs-number">16</span>,<span class="hljs-number">843</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> COMMIT
>>> </code>

此时真的写入数据库了哦。向课程表插入五条

<code class=" hljs python"><span class="hljs-prompt">>>> </span>cla = Cla(cname=<span class="hljs-string">'yuwen'</span>)
<span class="hljs-prompt">>>> </span>session.add(cla)
<span class="hljs-prompt">>>> </span>cla = Cla(cname=<span class="hljs-string">'shuxue'</span>)
<span class="hljs-prompt">>>> </span>session.add(cla)
<span class="hljs-prompt">>>> </span>cla = Cla(cname=<span class="hljs-string">'yingyu'</span>)
<span class="hljs-prompt">>>> </span>session.add(cla)
<span class="hljs-prompt">>>> </span>cla = Cla(cname=<span class="hljs-string">'wuli'</span>)
<span class="hljs-prompt">>>> </span>session.add(cla)
<span class="hljs-prompt">>>> </span>cla = Cla(cname=<span class="hljs-string">'huaxue'</span>)
<span class="hljs-prompt">>>> </span>session.add(cla)
<span class="hljs-prompt">>>> </span>session.commit()</code>

3,现在开始操作数据

<code class=" hljs vbnet">>>> query = session.query(Stu)
>>> <span class="hljs-keyword">for</span> st <span class="hljs-keyword">in</span> query:
...     print st.name
... 
对应的SQL语句
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">56</span>:<span class="hljs-number">07</span>,<span class="hljs-number">084</span> INFO sqlalchemy.engine.base.Engine ()
a
b
c
d
e
>>> print query.all()<span class="hljs-preprocessor"># # 返回的是一个类似列表的对象</span>
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">58</span>:<span class="hljs-number">16</span>,<span class="hljs-number">085</span> INFO sqlalchemy.engine.base.Engine ()
[<__main__.Stu <span class="hljs-built_in">object</span> at <span class="hljs-number">0xb66b3f4c</span>>, <__main__.Stu <span class="hljs-built_in">object</span> at <span class="hljs-number">0xb5e4202c</span>>, <__main__.Stu <span class="hljs-built_in">object</span> at <span class="hljs-number">0xb66b3f8c</span>>, <__main__.Stu <span class="hljs-built_in">object</span> at <span class="hljs-number">0xb5e4206c</span>>, <__main__.Stu <span class="hljs-built_in">object</span> at <span class="hljs-number">0xb6688c0c</span>>]

>>> print query.first().name<span class="hljs-preprocessor"># 有数据时返回第一条记录,没有数据时会返回 None</span>
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">18</span>:<span class="hljs-number">59</span>:<span class="hljs-number">43</span>,<span class="hljs-number">149</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">1</span>,)
a
<span class="hljs-preprocessor"># print query.one().name# 不存在,或有多行记录时会抛出异常</span>

>>> print query.filter(Stu.id == <span class="hljs-number">2</span>).first().name
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id = %s 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">04</span>:<span class="hljs-number">54</span>,<span class="hljs-number">363</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>, <span class="hljs-number">1</span>)
b
>>> print query.filter(<span class="hljs-comment">'id = 2').first().name # 支持字符串</span>
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> id = <span class="hljs-number">2</span> 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">07</span>:<span class="hljs-number">02</span>,<span class="hljs-number">016</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">1</span>,)
b
>>> print query.<span class="hljs-keyword">get</span>(<span class="hljs-number">2</span>).name <span class="hljs-preprocessor"># 以主键获取,等效于上句</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">07</span>:<span class="hljs-number">40</span>,<span class="hljs-number">007</span> INFO sqlalchemy.engine.base.Engine <span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">07</span>:<span class="hljs-number">40</span>,<span class="hljs-number">007</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>,)
b
>>> print query.<span class="hljs-keyword">get</span>(<span class="hljs-number">2</span>).id
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id, stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">08</span>:<span class="hljs-number">46</span>,<span class="hljs-number">009</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>,)
<span class="hljs-number">2</span></code>
<code class=" hljs avrasm">>>> quer2 = session<span class="hljs-preprocessor">.query</span>(Stu<span class="hljs-preprocessor">.name</span>)
>>> print quer2<span class="hljs-preprocessor">.all</span>() 
SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">09</span>:<span class="hljs-number">46</span>,<span class="hljs-number">259</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
[(<span class="hljs-string">'a'</span>,), (<span class="hljs-string">'b'</span>,), (<span class="hljs-string">'c'</span>,), (<span class="hljs-string">'d'</span>,), (<span class="hljs-string">'e'</span>,)]</code>
<code class=" hljs avrasm">>>> print quer2<span class="hljs-preprocessor">.limit</span>(<span class="hljs-number">1</span>)<span class="hljs-preprocessor">.all</span>() <span class="hljs-preprocessor">#只返回一条</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">11</span>:<span class="hljs-number">23</span>,<span class="hljs-number">383</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">11</span>:<span class="hljs-number">23</span>,<span class="hljs-number">383</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>,)
[(<span class="hljs-string">'a'</span>,)]

>>> print quer2<span class="hljs-preprocessor">.limit</span>(<span class="hljs-number">2</span>)<span class="hljs-preprocessor">.all</span>()<span class="hljs-preprocessor">#只返回两条</span>
SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">11</span>:<span class="hljs-number">29</span>,<span class="hljs-number">480</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">2</span>,)
[(<span class="hljs-string">'a'</span>,), (<span class="hljs-string">'b'</span>,)]</code>
<code class=" hljs avrasm">>>> print quer2<span class="hljs-preprocessor">.offset</span>(<span class="hljs-number">1</span>)<span class="hljs-preprocessor">.all</span>() <span class="hljs-preprocessor">#跳过一条,从第二条数据开始查询</span>
SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
 LIMIT %s, <span class="hljs-number">18446744073709551615</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">13</span>:<span class="hljs-number">25</span>,<span class="hljs-number">734</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>,)
[(<span class="hljs-string">'b'</span>,), (<span class="hljs-string">'c'</span>,), (<span class="hljs-string">'d'</span>,), (<span class="hljs-string">'e'</span>,)]
>>> print quer2<span class="hljs-preprocessor">.offset</span>(<span class="hljs-number">3</span>)<span class="hljs-preprocessor">.all</span>() <span class="hljs-preprocessor">#从第四条数据开始</span>
SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
 LIMIT %s, <span class="hljs-number">18446744073709551615</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">13</span>:<span class="hljs-number">39</span>,<span class="hljs-number">629</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">3</span>,)
[(<span class="hljs-string">'d'</span>,), (<span class="hljs-string">'e'</span>,)]</code>
<code class=" hljs oxygene">#按name降序排序
>>> print quer2.order_by(Stu.name.<span class="hljs-keyword">desc</span>()).all()
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> stu.name <span class="hljs-keyword">DESC</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">16</span>:<span class="hljs-number">56</span>,<span class="hljs-number">022</span> INFO sqlalchemy.engine.base.Engine ()
[(<span class="hljs-string">'e'</span>,), (<span class="hljs-string">'d'</span>,), (<span class="hljs-string">'c'</span>,), (<span class="hljs-string">'b'</span>,), (<span class="hljs-string">'a'</span>,)]

>>> print quer2.order_by(<span class="hljs-string">'name desc'</span>).all()
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> name <span class="hljs-keyword">desc</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">17</span>:<span class="hljs-number">09</span>,<span class="hljs-number">851</span> INFO sqlalchemy.engine.base.Engine ()
[(<span class="hljs-string">'e'</span>,), (<span class="hljs-string">'d'</span>,), (<span class="hljs-string">'c'</span>,), (<span class="hljs-string">'b'</span>,), (<span class="hljs-string">'a'</span>,)]
#按name降序,有重复的按id升序排序
>>> print session.query(Stu.id).order_by(<span class="hljs-string">'name desc'</span>,<span class="hljs-string">'id'</span>).all()
<span class="hljs-keyword">SELECT</span> stu.id <span class="hljs-keyword">AS</span> stu_id 
<span class="hljs-keyword">FROM</span> stu <span class="hljs-keyword">ORDER</span> <span class="hljs-keyword">BY</span> name <span class="hljs-keyword">desc</span>, stu.id
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">20</span>:<span class="hljs-number">34</span>,<span class="hljs-number">818</span> INFO sqlalchemy.engine.base.Engine ()
[(<span class="hljs-number">5</span>L,), (<span class="hljs-number">4</span>L,), (<span class="hljs-number">3</span>L,), (<span class="hljs-number">2</span>L,), (<span class="hljs-number">1</span>L,)]</code>
<code class=" hljs vbnet"><span class="hljs-preprocessor">#scalar()在有多条数据时使用报出异常,all()可以使用多条也可以使用一条</span>
<span class="hljs-preprocessor">#>>> print quer2.filter(Stu.id>2).scalar()</span>
>>> print quer2.filter(Stu.id><span class="hljs-number">2</span>).all()
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id > %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">56</span>:<span class="hljs-number">47</span>,<span class="hljs-number">760</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>,)
[(<span class="hljs-comment">'c',), ('d',), ('e',)]</span>

>>> print quer2.filter(Stu.id==<span class="hljs-number">2</span>).all()
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">57</span>:<span class="hljs-number">47</span>,<span class="hljs-number">901</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>,)
[(<span class="hljs-comment">'b',)]</span>


>>> print quer2.filter(Stu.id==<span class="hljs-number">2</span>).scalar()
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">23</span>:<span class="hljs-number">38</span>,<span class="hljs-number">761</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">2</span>,)
b

>>> print quer2.filter(<span class="hljs-comment">'id=2').scalar()</span>
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> id=<span class="hljs-number">2</span>
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">43</span>:<span class="hljs-number">47</span>,<span class="hljs-number">797</span> INFO sqlalchemy.engine.base.Engine ()
b

<span class="hljs-preprocessor">#在此中‘,’等价于and</span>
>>> print query2.filter(Stu.id><span class="hljs-number">1</span>,Stu.name !=<span class="hljs-comment">'a').first()</span>
<span class="hljs-keyword">SELECT</span> stu.name <span class="hljs-keyword">AS</span> stu_name 
<span class="hljs-keyword">FROM</span> stu 
<span class="hljs-keyword">WHERE</span> stu.id > %s <span class="hljs-keyword">AND</span> stu.name != %s 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">51</span>:<span class="hljs-number">14</span>,<span class="hljs-number">571</span> INFO sqlalchemy.engine.base.Engine (<span class="hljs-number">1</span>, <span class="hljs-comment">'a', 1)</span>
(<span class="hljs-comment">'b',)</span>
>>> 
</code>
<code class=" hljs avrasm"><span class="hljs-preprocessor">#此种迭代也类似与and</span>
>>> query3 = query2<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.id</span>><span class="hljs-number">1</span>)
>>> query3 = query3<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.name</span> != <span class="hljs-string">'a'</span>)
>>> query3<span class="hljs-preprocessor">.first</span>()
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">53</span>:<span class="hljs-number">50</span>,<span class="hljs-number">150</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.id</span> > %s <span class="hljs-keyword">AND</span> stu<span class="hljs-preprocessor">.name</span> != %s 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">53</span>:<span class="hljs-number">50</span>,<span class="hljs-number">151</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>, <span class="hljs-string">'a'</span>, <span class="hljs-number">1</span>)
(<span class="hljs-string">'b'</span>,)
</code>
<code class=" hljs avrasm"><span class="hljs-preprocessor">#or_就是类似or</span>
>>> print query2<span class="hljs-preprocessor">.filter</span>(or_(Stu<span class="hljs-preprocessor">.id</span> == <span class="hljs-number">1</span>,Stu<span class="hljs-preprocessor">.id</span>==<span class="hljs-number">2</span>))<span class="hljs-preprocessor">.all</span>()
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">55</span>:<span class="hljs-number">59</span>,<span class="hljs-number">383</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.id</span> = %s <span class="hljs-keyword">OR</span> stu<span class="hljs-preprocessor">.id</span> = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">19</span>:<span class="hljs-number">55</span>:<span class="hljs-number">59</span>,<span class="hljs-number">383</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>, <span class="hljs-number">2</span>)
[(<span class="hljs-string">'a'</span>,), (<span class="hljs-string">'b'</span>,)]
</code>
<code class=" hljs avrasm"><span class="hljs-preprocessor"># in的用法</span>
>>> print query2<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.id</span><span class="hljs-preprocessor">.in</span>_((<span class="hljs-number">1</span>,<span class="hljs-number">2</span>,<span class="hljs-number">3</span>)))<span class="hljs-preprocessor">.all</span>()
SELECT stu<span class="hljs-preprocessor">.name</span> AS stu_name 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.id</span> <span class="hljs-keyword">IN</span> (%s, %s, %s)
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">01</span>:<span class="hljs-number">01</span>,<span class="hljs-number">729</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>)
[(<span class="hljs-string">'a'</span>,), (<span class="hljs-string">'b'</span>,), (<span class="hljs-string">'c'</span>,)]
>>> 
</code>
<code class=" hljs python"><span class="hljs-comment">#为null的一些用法</span>
<span class="hljs-prompt">>>> </span>query4 = session.query(Stu.id)
<span class="hljs-prompt">>>> </span><span class="hljs-keyword">print</span> query4.filter(Stu.name==<span class="hljs-keyword">None</span>).scalar()
SELECT stu.id AS stu_id 
FROM stu 
WHERE stu.name IS NULL
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">02</span>:<span class="hljs-number">59</span>,<span class="hljs-number">821</span> INFO sqlalchemy.engine.base.Engine ()
<span class="hljs-keyword">None</span>
<span class="hljs-prompt">>>> </span>
<span class="hljs-prompt">>>> </span><span class="hljs-keyword">print</span> query4.filter(<span class="hljs-string">'name is null'</span>).scalar()
SELECT stu.id AS stu_id 
FROM stu 
WHERE name <span class="hljs-keyword">is</span> null
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">03</span>:<span class="hljs-number">40</span>,<span class="hljs-number">312</span> INFO sqlalchemy.engine.base.Engine ()
<span class="hljs-keyword">None</span>
<span class="hljs-prompt">>>> </span>
</code>
<code class=" hljs avrasm"><span class="hljs-preprocessor">#不为null的一些用法</span>
>>> print query4<span class="hljs-preprocessor">.filter</span>(not_(Stu<span class="hljs-preprocessor">.name</span> == None))<span class="hljs-preprocessor">.all</span>()
SELECT stu<span class="hljs-preprocessor">.id</span> AS stu_id 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.name</span> IS NOT NULL
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">04</span>:<span class="hljs-number">49</span>,<span class="hljs-number">888</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
[(<span class="hljs-number">1</span>L,), (<span class="hljs-number">2</span>L,), (<span class="hljs-number">3</span>L,), (<span class="hljs-number">4</span>L,), (<span class="hljs-number">5</span>L,)]
>>> 

>>> print query4<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.name</span> != None)<span class="hljs-preprocessor">.all</span>()
SELECT stu<span class="hljs-preprocessor">.id</span> AS stu_id 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.name</span> IS NOT NULL
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">05</span>:<span class="hljs-number">42</span>,<span class="hljs-number">724</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
[(<span class="hljs-number">1</span>L,), (<span class="hljs-number">2</span>L,), (<span class="hljs-number">3</span>L,), (<span class="hljs-number">4</span>L,), (<span class="hljs-number">5</span>L,)]
>>> </code>
<code class=" hljs avrasm"><span class="hljs-preprocessor">#func条用各种函数的用法</span>

>>> print query4<span class="hljs-preprocessor">.count</span>()
SELECT count(*) AS count_1 
FROM (SELECT stu<span class="hljs-preprocessor">.id</span> AS stu_id 
FROM stu) AS anon_1
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">352</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
<span class="hljs-number">5</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.count</span>(<span class="hljs-string">'*'</span>))<span class="hljs-preprocessor">.select</span>_from(Stu)<span class="hljs-preprocessor">.scalar</span>()
 SELECT count(%s) AS count_1 
FROM stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">356</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'*'</span>,)
<span class="hljs-number">5</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.count</span>(<span class="hljs-string">'1'</span>))<span class="hljs-preprocessor">.select</span>_from(Stu)<span class="hljs-preprocessor">.scalar</span>()
SELECT count(%s) AS count_1 
FROM stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">362</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'1'</span>,)
<span class="hljs-number">5</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.count</span>(Stu<span class="hljs-preprocessor">.id</span>))<span class="hljs-preprocessor">.scalar</span>()
SELECT count(stu<span class="hljs-preprocessor">.id</span>) AS count_1 
FROM stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">369</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
<span class="hljs-number">5</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.count</span>(<span class="hljs-string">'*'</span>))<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.id</span> > <span class="hljs-number">0</span>)<span class="hljs-preprocessor">.scalar</span>() <span class="hljs-preprocessor"># filter()中包含Stu,因此不需要指定表</span>
SELECT count(%s) AS count_1 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.id</span> > %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">377</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'*'</span>, <span class="hljs-number">0</span>)
<span class="hljs-number">5</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.count</span>(<span class="hljs-string">'*'</span>))<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.name</span> == <span class="hljs-string">'a'</span>)<span class="hljs-preprocessor">.limit</span>(<span class="hljs-number">1</span>)<span class="hljs-preprocessor">.scal</span>() == <span class="hljs-number">1</span> <span class="hljs-preprocessor"># 可以用 limit() 限制 count() 的返回数</span>
SELECT count(%s) AS count_1 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.name</span> = %s 
 LIMIT %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">394</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-string">'*'</span>, <span class="hljs-string">'a'</span>, <span class="hljs-number">1</span>)
True

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.sum</span>(Stu<span class="hljs-preprocessor">.id</span>))<span class="hljs-preprocessor">.scalar</span>()
SELECT sum(stu<span class="hljs-preprocessor">.id</span>) AS sum_1 
FROM stu
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">401</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
<span class="hljs-number">15</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.now</span>())<span class="hljs-preprocessor">.scalar</span>() <span class="hljs-preprocessor"># func 后可以跟任意函数名,只要该据库支持</span>
SELECT now() AS now_1
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">406</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.current</span>_timestamp())<span class="hljs-preprocessor">.scalar</span>()
SELECT CURRENT_TIMESTAMP AS current_timestamp_1
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>,<span class="hljs-number">411</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> ()
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">43</span>

>>> print session<span class="hljs-preprocessor">.query</span>(func<span class="hljs-preprocessor">.md</span>5(Stu<span class="hljs-preprocessor">.name</span>))<span class="hljs-preprocessor">.filter</span>(Stu<span class="hljs-preprocessor">.id</span> == <span class="hljs-number">1</span>)<span class="hljs-preprocessor">.scalar</span>()
SELECT md5(stu<span class="hljs-preprocessor">.name</span>) AS md5_1 
FROM stu 
WHERE stu<span class="hljs-preprocessor">.id</span> = %s
<span class="hljs-number">2016</span>-<span class="hljs-number">05</span>-<span class="hljs-number">09</span> <span class="hljs-number">20</span>:<span class="hljs-number">08</span>:<span class="hljs-number">44</span>,<span class="hljs-number">841</span> INFO sqlalchemy<span class="hljs-preprocessor">.engine</span><span class="hljs-preprocessor">.base</span><span class="hljs-preprocessor">.Engine</span> (<span class="hljs-number">1</span>,)
<span class="hljs-number">0</span>cc175b9c0f1b6a831c399e269772661
>>> 
</code>
<code class=" hljs asciidoc">#修改数据
>>> query.filter(Stu.id==1).update({Stu.name:<span class="hljs-emphasis">'li'</span>})
UPDATE stu SET name=%s WHERE stu.id = %s
2016-05-09 20:12:57,027 INFO sqlalchemy.engine.base.Engine (<span class="hljs-emphasis">'li'</span>, 1)
1L

#删除数据
>>> query = session.query(Grade)
>>> query.filter(Grade.id == 1).delete()
DELETE FROM grade WHERE grade.id = %s
2016-05-09 20:28:18,638 INFO sqlalchemy.engine.base.Engine (1,)
1L
>>> 
此时没有提交,在数据库中环视存在的
<span class="hljs-header">mysql> select * from grade;
+----+------+------+------+</span>
<span class="hljs-header">| id | uid  | cid  | gre  |
+----+------+------+------+</span>
|  1 |    1 |    1 |   60 |
|  2 |    2 |    1 |   66 |
|  3 |    5 |    1 |   66 |
|  4 |    5 |    5 |   96 |
|  5 |    5 |    3 |   96 |
|  6 |    3 |    2 |   96 |
|  7 |    3 |    4 |   76 |
|  8 |    4 |    4 |   76 |
|  9 |    4 |    3 |   76 |
| 10 |    4 |    5 |   76 |
| 11 |    1 |    4 |   76 |
| 12 |    1 |    5 |   76 |
| 13 |    2 |    5 |   76 |
| 14 |    3 |    3 |   60 |
<span class="hljs-header">| 15 |    2 |    3 |   50 |
+----+------+------+------+</span>
15 rows in set (0.00 sec)
#开始提交
>>> session.commit()
2016-05-09 20:31:02,461 INFO sqlalchemy.engine.base.Engine COMMIT
>>> 
<span class="hljs-header">mysql> select * from grade;
+----+------+------+------+</span>
<span class="hljs-header">| id | uid  | cid  | gre  |
+----+------+------+------+</span>
|  2 |    2 |    1 |   66 |
|  3 |    5 |    1 |   66 |
|  4 |    5 |    5 |   96 |
|  5 |    5 |    3 |   96 |
|  6 |    3 |    2 |   96 |
|  7 |    3 |    4 |   76 |
|  8 |    4 |    4 |   76 |
|  9 |    4 |    3 |   76 |
| 10 |    4 |    5 |   76 |
| 11 |    1 |    4 |   76 |
| 12 |    1 |    5 |   76 |
| 13 |    2 |    5 |   76 |
| 14 |    3 |    3 |   60 |
<span class="hljs-header">| 15 |    2 |    3 |   50 |
+----+------+------+------+</span>
14 rows in set (0.00 sec)

也获取不到对象了
>>> print query.get(1)
SELECT grade.id AS grade<span class="hljs-emphasis">_id, grade.uid AS grade_</span>uid, grade.cid AS grade<span class="hljs-emphasis">_cid, grade.gre AS grade_</span>gre 
FROM grade 
WHERE grade.id = %s
2016-05-09 20:32:20,742 INFO sqlalchemy.engine.base.Engine (1,)
None
>>> </code>

单表的增删改查完事了,下面来看看多表连接操作
http://blog.csdn.net/u011573853/article/details/51363780
一些细节会在下面进行说明(事务,加锁,编码等)
http://blog.csdn.net/u011573853/article/details/51366124

陳述
本文內容由網友自願投稿,版權歸原作者所有。本站不承擔相應的法律責任。如發現涉嫌抄襲或侵權的內容,請聯絡admin@php.cn
您如何處理MySQL中的數據庫升級?您如何處理MySQL中的數據庫升級?Apr 30, 2025 am 12:28 AM

MySQL數據庫升級的步驟包括:1.備份數據庫,2.停止當前MySQL服務,3.安裝新版本MySQL,4.啟動新版本MySQL服務,5.恢復數據庫。升級過程需注意兼容性問題,並可使用高級工具如PerconaToolkit進行測試和優化。

您可以使用MySQL的不同備份策略是什麼?您可以使用MySQL的不同備份策略是什麼?Apr 30, 2025 am 12:28 AM

MySQL備份策略包括邏輯備份、物理備份、增量備份、基於復制的備份和雲備份。 1.邏輯備份使用mysqldump導出數據庫結構和數據,適合小型數據庫和版本遷移。 2.物理備份通過複製數據文件,速度快且全面,但需數據庫一致性。 3.增量備份利用二進制日誌記錄變化,適用於大型數據庫。 4.基於復制的備份通過從服務器備份,減少對生產系統的影響。 5.雲備份如AmazonRDS提供自動化解決方案,但成本和控制需考慮。選擇策略時應考慮數據庫大小、停機容忍度、恢復時間和恢復點目標。

什麼是mySQL聚類?什麼是mySQL聚類?Apr 30, 2025 am 12:28 AM

MySQLclusteringenhancesdatabaserobustnessandscalabilitybydistributingdataacrossmultiplenodes.ItusestheNDBenginefordatareplicationandfaulttolerance,ensuringhighavailability.Setupinvolvesconfiguringmanagement,data,andSQLnodes,withcarefulmonitoringandpe

如何優化數據庫架構設計以在MySQL中的性能?如何優化數據庫架構設計以在MySQL中的性能?Apr 30, 2025 am 12:27 AM

在MySQL中優化數據庫模式設計可通過以下步驟提升性能:1.索引優化:在常用查詢列上創建索引,平衡查詢和插入更新的開銷。 2.表結構優化:通過規範化或反規範化減少數據冗餘,提高訪問效率。 3.數據類型選擇:使用合適的數據類型,如INT替代VARCHAR,減少存儲空間。 4.分區和分錶:對於大數據量,使用分區和分錶分散數據,提升查詢和維護效率。

您如何優化MySQL性能?您如何優化MySQL性能?Apr 30, 2025 am 12:26 AM

tooptimizemysqlperformance,lofterTheSeSteps:1)inasemproperIndexingTospeedUpqueries,2)使用ExplaintplaintoAnalyzeandoptimizequeryPerformance,3)ActiveServerConfigurationStersLikeTlikeTlikeTlikeIkeLikeIkeIkeLikeIkeLikeIkeLikeIkeLikeNodb_buffer_pool_sizizeandmax_connections,4)

如何使用MySQL的函數進行數據處理和計算如何使用MySQL的函數進行數據處理和計算Apr 29, 2025 pm 04:21 PM

MySQL函數可用於數據處理和計算。 1.基本用法包括字符串處理、日期計算和數學運算。 2.高級用法涉及結合多個函數實現複雜操作。 3.性能優化需避免在WHERE子句中使用函數,並使用GROUPBY和臨時表。

MySQL批量插入數據的高效方法MySQL批量插入數據的高效方法Apr 29, 2025 pm 04:18 PM

MySQL批量插入数据的高效方法包括:1.使用INSERTINTO...VALUES语法,2.利用LOADDATAINFILE命令,3.使用事务处理,4.调整批量大小,5.禁用索引,6.使用INSERTIGNORE或INSERT...ONDUPLICATEKEYUPDATE,这些方法能显著提升数据库操作效率。

給MySQL表添加和刪除字段的操作步驟給MySQL表添加和刪除字段的操作步驟Apr 29, 2025 pm 04:15 PM

在MySQL中,添加字段使用ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column,刪除字段使用ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop。添加字段時,需指定位置以優化查詢性能和數據結構;刪除字段前需確認操作不可逆;使用在線DDL、備份數據、測試環境和低負載時間段修改表結構是性能優化和最佳實踐。

See all articles

熱AI工具

Undresser.AI Undress

Undresser.AI Undress

人工智慧驅動的應用程序,用於創建逼真的裸體照片

AI Clothes Remover

AI Clothes Remover

用於從照片中去除衣服的線上人工智慧工具。

Undress AI Tool

Undress AI Tool

免費脫衣圖片

Clothoff.io

Clothoff.io

AI脫衣器

Video Face Swap

Video Face Swap

使用我們完全免費的人工智慧換臉工具,輕鬆在任何影片中換臉!

熱工具

ZendStudio 13.5.1 Mac

ZendStudio 13.5.1 Mac

強大的PHP整合開發環境

mPDF

mPDF

mPDF是一個PHP庫,可以從UTF-8編碼的HTML產生PDF檔案。原作者Ian Back編寫mPDF以從他的網站上「即時」輸出PDF文件,並處理不同的語言。與原始腳本如HTML2FPDF相比,它的速度較慢,並且在使用Unicode字體時產生的檔案較大,但支援CSS樣式等,並進行了大量增強。支援幾乎所有語言,包括RTL(阿拉伯語和希伯來語)和CJK(中日韓)。支援嵌套的區塊級元素(如P、DIV),

SecLists

SecLists

SecLists是最終安全測試人員的伙伴。它是一個包含各種類型清單的集合,這些清單在安全評估過程中經常使用,而且都在一個地方。 SecLists透過方便地提供安全測試人員可能需要的所有列表,幫助提高安全測試的效率和生產力。清單類型包括使用者名稱、密碼、URL、模糊測試有效載荷、敏感資料模式、Web shell等等。測試人員只需將此儲存庫拉到新的測試機上,他就可以存取所需的每種類型的清單。

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

將Eclipse與SAP NetWeaver應用伺服器整合。

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

這個專案正在遷移到osdn.net/projects/mingw的過程中,你可以繼續在那裡關注我們。 MinGW:GNU編譯器集合(GCC)的本機Windows移植版本,可自由分發的導入函式庫和用於建置本機Windows應用程式的頭檔;包括對MSVC執行時間的擴展,以支援C99功能。 MinGW的所有軟體都可以在64位元Windows平台上運作。