1.1.2.删除数据库。 语法:drop database 代码: //删除数据库hr drop database hr //如果存在hr数据库,则删除数据库hr IF DB_ID('hr') IS NOT NULL DROP DATABASE TestDB ----------------------------------------------------------- 1.2备份与恢复backup/restore database 1.2.1.添加备份设备 语法:sp_addumpdevice
//子句说明 select子句:指出检索的数据项 from 子句:指出检索的数据表 where 子句:指出检索的数据条件 group by子句:指出检索的数据进行汇总 having子句:指出检索的数据进行汇总之前的条件 order by子句:指出检索的数据条件进行排序 代码: //所有字段方式显示orders全部记录 select * from orders //按字段显示全部记录 select order_num,order_date,amount from orders //按字段显示全部记录,但除掉重复的记录 select order_num,order_date,amount from orders //用sql-expression乘运算计算列 select amount,amount*0.08 as discount_amt from orders //用自定义函数计算指定列 select order_num,order_date,amount,f_amt_to_chn(amount) as 金额 from orders
select选项太多,代码例子就省略... ----------------------------------------------------------- 2.2子查询 Sub Query 语法:select ... from where / having column 测试条件 (Sub Query) //测试条件 比较测试条件(=,,>,=,范围测试条件(betweeen 下限值 and 上限值) 成员测试条件(in,not in) 存在测试条件(exists,not exists) 匹配测试条件(like) 限定测试条件(any,all) 空值测试条件(is null)
代码: //列出没有完成销售目标10%的销售人员清单[select name from salesreps where quota //列出公司的销售目标超过各个销售人员定额总和的销售点[>测试] select city from offices where target > (select sum(quota) from salesreps where rep_office=office) //列出超过销售目标的销售点的业务人员[in测试] select name from salesreps where office in (select office from offies where sales > target) //列出订单大于2500元的产品名称[exists测试] select description from products where exists ( select * from orders where product=prodct_id and amount > 2500.00 ) //列出完成销售目标10%的销售人员清单[any测试] select name from salesreps where (0.1* quota) ----------------------------------------------------------- 2.3连接查询Table Joins 多表连接类型可分为三类(内/外/交叉连接) 主从表或者父子表进行多表连接多以主键和外键进行关联 Outer joins(LEFT OUTER, RIGHT OUTER, and FULL OUTER joins) left outer join:查询的结果以左边表行数为准 right outer join:查询的结果以右边表行数为准
2.3.1.内连接inner join 功能: 语法: SELECT select_list FROM table_1 [INNER] JOIN table_2 ON join_condition_1 [[INNER] JOIN table_3 ON join_condition_2]... 代码: //没有where子句的内连接 SELECT * FROM Products INNER JOIN Suppliers ON Products.SupplierID = Suppliers.SupplierID
//有where子句的内连接 SELECT p.ProductID, s.SupplierID, p.ProductName, s.CompanyName FROM Products p INNER JOIN Suppliers s ON p.SupplierID = s.SupplierID WHERE p.ProductID ----------------------------------------------------------- 2.3.2.外连接outer join 功能:包括三种连接LEFT OUTER, RIGHT OUTER, and FULL OUTER joins left outer :查询的结果以左边表行数为准 right outer :查询的结果以右边表行数为准 语法:select ... from table1 [left/right/full outer join ]table2 where ... 代码: //以Customers表行数为标准去连接Orders表 SELECT c.CustomerID, CompanyName FROM Customers c LEFT OUTER JOIN Orders o ON c.CustomerID = o.CustomerID WHERE o.CustomerID IS NULL
----------------------------------------------------------- 2.3.3.交叉连接cross join 功能:以主从表或者父子表之间的主键进行连接,最终以笛卡尔乘积运算的结果 语法:select ... from table1 cross join table2 where ...
代码: //显示结果以表1行数*表2行数 假设Departments为4行记录 假设Jobs为3行记录 下面的显示结果为4*3=12行记录 SELECT deptname,jobdesc FROM Departments CROSS JOIN Jobs //用关键字匹配的交叉连接 oc_head/oc_detail是主从表 oc_head(主键oc_number) oc_detail(主键oc_number,item_number,ship_date)
SELECT h.customerid,d.item_number,d.ship_date from oc_head as h CROSS JOIN oc_detail as d where h.oc_number=d.oc_number ----------------------------------------------------------- 2.4汇总查询Group Query //汇总查询相当于会计报表中的小计汇总的功能
语法: select ... from group by [having search expression]
代码: //求出每名销售人员的销售金额 select rep,sum(amount) from orders group by rep //每个销售点分配了多少销售人员 select rep_office,count(*) from salesreps group by rep_office //计算每名销售人员的每个客户和订单金额 select cust,rep,sum(amount) from orders group by cust,rep //Having子句应用 select rep,avg(amount) from orders having sum(quota) > 3000.00
/**********************************************************/ 3.数据修改DATA MODIFY LANGUAGE 3.1插入数据Insert 3.2修改数据Update 3.3删除数据Delete ----------------------------------------------------------- 3.1插入数据Insert 3.1.1.单行插入 语法:insert into [...] values(...);
代码: //不省略字段清单 insert into salesreps(name,age,empl_no,sales,title,hire_date,rep_office) values('jack toms',36,111,0.00,'sales mgr','10-05-2010',13) //省略字段清单 insert into salesreps values('jack toms',36,111,0.00,'sales mgr','10-05-2010',13) 3.1.2.多行插入 语法:insert into [(...)] values(...)
Déclaration:
Le contenu de cet article est volontairement contribué par les internautes et les droits d'auteur appartiennent à l'auteur original. Ce site n'assume aucune responsabilité légale correspondante. Si vous trouvez un contenu suspecté de plagiat ou de contrefaçon, veuillez contacter admin@php.cn