MySQL怎麼進行單表查詢？單表查詢的語句
- 青灯夜游轉載
- 2018-10-27 16:56:512691瀏覽
這篇文章帶給大家的內容是介紹MySQL怎麼進行單表查詢？單表查詢的語句。有一定的參考價值，有需要的朋友可以參考一下，希望對你們有幫助。
先建立資料表
# 创建表
mysql> create table company.employee5(
id int primary key AUTO_INCREMENT not null,
name varchar(30) not null,
sex enum('male','female') default 'male' not null,
hire_date date not null,
post varchar(50) not null,
job_description varchar(100),
salary double(15,2) not null,
office int,
dep_id int
);
# 插入数据
mysql> insert into company.employee5(name,sex,hire_date,post,job_description,salary,office,dep_id) values
('jack','male','20180202','instructor','teach',5000,501,100),
('tom','male','20180203','instructor','teach',5500,501,100),
('robin','male','20180202','instructor','teach',8000,501,100),
('alice','female','20180202','instructor','teach',7200,501,100),
('tianyun','male','20180202','hr','hrcc',600,502,101),
('harry','male','20180202','hr',NULL,6000,502,101),
('emma','female','20180206','sale','salecc',20000,503,102),
('christine','female','20180205','sale','salecc',2200,503,102),
('zhuzhu','male','20180205','sale',NULL,2200,503,102),
('gougou','male','20180205','sale','',2200,503,102);
# 查看表结构
mysql> desc employee5;
+-----------------+-----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+-----------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(30) | NO | | NULL | |
| sex | enum('male','female') | NO | | male | |
| hire_date | date | NO | | NULL | |
| post | varchar(50) | NO | | NULL | |
| job_description | varchar(100) | YES | | NULL | |
| salary | double(15,2) | NO | | NULL | |
| office | int(11) | YES | | NULL | |
| dep_id | int(11) | YES | | NULL | |
+-----------------+-----------------------+------+-----+---------+----------------+
#查詢語法##SELECT 字段1,字段2... FROM 表名
WHERE 条件
GROUP BY field
HAVING 筛选
ORDER BY field
LIMIT 限制条数；
查看表中所有資料mysql> select * from employee5;
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
| 1 | jack | male | 2018-02-02 | instructor | teach | 5000.00 | 501 | 100 |
| 2 | tom | male | 2018-02-03 | instructor | teach | 5500.00 | 501 | 100 |
| 3 | robin | male | 2018-02-02 | instructor | teach | 8000.00 | 501 | 100 |
| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
| 5 | tianyun | male | 2018-02-02 | hr | hrcc | 600.00 | 502 | 101 |
| 6 | harry | male | 2018-02-02 | hr | NULL | 6000.00 | 502 | 101 |
| 7 | emma | female | 2018-02-06 | sale | salecc | 20000.00 | 503 | 102 |
| 8 | christine | female | 2018-02-05 | sale | salecc | 2200.00 | 503 | 102 |
| 9 | zhuzhu | male | 2018-02-05 | sale | NULL | 2200.00 | 503 | 102 |
| 10 | gougou | male | 2018-02-05 | sale | | 2200.00 | 503 | 102 |
+----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
10 rows in set (0.00 sec)
#簡單查詢
#簡單查詢
mysql> SELECT * FROM employee5;
mysql> SELECT name, salary, dep_id FROM employee5;
去重DISTINCTmysql> SELECT post FROM employee5;
mysql> SELECT DISTINCT post FROM employee5;
注：不能部分使用DISTINCT，通常仅用于某一字段。
透過四則運算查詢 mysql> SELECT name, salary, salary*14 FROM employee5;
mysql> SELECT name, salary, salary*14 AS Annual_salary FROM employee5;
mysql> SELECT name, salary, salary*14 Annual_salary FROM employee5;
定義顯示格式CONCAT() 函数用于连接字符串
mysql> SELECT CONCAT(name, ' annual salary: ', salary*14) AS Annual_salary FROM employee5;
條件查詢a、语法
select * from 表名 where 条件
b、比较运算符
大于 小于 大于等于 小于等于 不等于 > < >= <= !=或<>
c、逻辑运算符
并且 或者 非 and or not
d、模糊查询
like % 表示任意多个任意字符
_ 表示一个任意字符
e、范围查询 in 表示在一个非连续的范围内
between...and... 表示在一个连续的范围内
f、空判断
判断空：is null
判断非空：is not null
g、优先级
小括号,not 比较运算符， 逻辑运算符
and比or优先级高，如果同时出现并希望先选or，需要结合()来使用
單一條件查詢mysql> SELECT name,post FROM employee5 WHERE post='hr';
#多條件查詢
mysql> SELECT name,salary FROM employee5 WHERE post='hr' AND salary>5000;
關鍵字BETWEEN AND查詢mysql> SELECT name,salary FROM employee5 WHERE salary BETWEEN 5000 AND 15000;
mysql> SELECT name,salary FROM employee5 WHERE salary NOT BETWEEN 5000 AND 15000;
關鍵字IS NULL 查詢mysql> SELECT name,job_description FROM employee5 WHERE job_description IS NULL;
mysql> SELECT name,job_description FROM employee5 WHERE job_description IS NOT NULL;
mysql> SELECT name,job_description FROM employee5 WHERE job_description='';
關鍵字IN集合查詢mysql> SELECT name, salary FROM employee5 WHERE salary=4000 OR salary=5000 OR salary=6000 OR salary=9000 ;
mysql> SELECT name, salary FROM employee5 WHERE salary IN (4000,5000,6000,9000) ;
mysql> SELECT name, salary FROM employee5 WHERE salary NOT IN (4000,5000,6000,9000) ;
關鍵字LIKE模糊查詢
#通配符’%’
mysql> SELECT * FROM employee5 WHERE name LIKE 'al%';
通配符’_’
mysql> SELECT * FROM employee5 WHERE name LIKE 'al___';
##查詢排序
##依單列排序
mysql> SELECT * FROM employee5 ORDER BY salary; mysql> SELECT name, salary FROM employee5 ORDER BY salary ASC; mysql> SELECT name, salary FROM employee5 ORDER BY salary DESC;依多列排序
mysql> SELECT * FROM employee5 ORDER BY hire_date DESC,salary ASC;
# 先按入职时间，再按薪水排序
mysql> SELECT * FROM employee5 ORDER BY hire_date DESC, salary DESC;
# 先按职位，再按薪水排序
mysql> SELECT * FROM employee5 ORDER BY post, salary DESC;
分頁查詢limit
###mysql> SELECT * FROM employee5 ORDER BY salary DESC LIMIT 5; //默认初始位置为0 mysql> SELECT * FROM employee5 ORDER BY salary DESC LIMIT 0,5; mysql> SELECT * FROM employee5 ORDER BY salary DESC LIMIT 3,5; //从第4条开始，共显示5条##########聚合函數查詢#########
a、count(*) 表示计算总行数，括号中可以写*和列名 b、max(列) 表示求此列的最大值 c、min(列) 表示求此列的最小值 d、sun(列) 表示求此列的和 e、avg(列) 表示求此列的平均值 mysql> SELECT COUNT(*) FROM employee5; mysql> SELECT COUNT(*) FROM employee5 WHERE dep_id=101; mysql> SELECT MAX(salary) FROM employee5; mysql> SELECT MIN(salary) FROM employee5; mysql> SELECT AVG(salary) FROM employee5; mysql> SELECT SUM(salary) FROM employee5; mysql> SELECT SUM(salary) FROM employee5 WHERE dep_id=101;######################################################################################################################## ##分組查詢#########
单独使用GROUP BY关键字分组 mysql> SELECT post FROM employee5 GROUP BY post; 注意：我们按照post字段分组，那么select查询的字段只能是post，想要获取组内的其他相关信息，需要借助函数#########GROUP BY關鍵字和group_concat()函數一起使用#########
# 按照id分组，并查看组内成员 mysql> SELECT dep_id,GROUP_CONCAT(name) FROM employee5 GROUP BY dep_id; mysql> SELECT dep_id,GROUP_CONCAT(name) as emp_members FROM employee5 GROUP BY dep_id;####### ###GROUP BY和集合函數一起使用#########
# 按照dep_id 分组， 并计算组内成员工资总和 mysql> SELECT dep_id,SUM(salary) FROM employee5 GROUP BY dep_id; # 按照dep_id分组，并计算组内成员工资平均值 mysql> SELECT dep_id,AVG(salary) FROM employee5 GROUP BY dep_id;##########正規表示式查詢########
mysql> SELECT * FROM employee5 WHERE name REGEXP '^j';
mysql> SELECT * FROM employee5 WHERE salary REGEXP '[5]+.*';
mysql> SELECT * FROM employee5 WHERE salary REGEXP '[5]{2}.*';以上是MySQL怎麼進行單表查詢？單表查詢的語句的詳細內容。更多資訊請關注PHP中文網其他相關文章！
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