SQL Server 语句大全（2）-------流程控制语句

流程控制语句 

 

IF ELSE 语句

用法如下：

 

declare @x int @y int @z int select @x = 1 @y = 2 @z=3 if @x > @y print 'x > y' --打印字符串'x > y' else if @y > @z print 'y > z' else print 'z > y' 

CASE 语句

用法如下：

use pangu update employee set e_wage = case when job_level = ‟1‟ then e_wage*1.08 when job_level = ‟2‟ then e_wage*1.07 when job_level = ‟3‟ then e_wage*1.06 else e_wage*1.05 end 

 

WHILE CONTINUE BREAK

用法如下：

 

declare @x int @y int @c int select @x = 1 @y=1 while @x < 3 begin print @x --打印变量 x  的值 while @y < 3 begin select @c = 100*@x + @y print @c --打印变量 c  的值 select @y = @y + 1 end select @x = @x + 1 select @y = 1 end 

WAITFOR

用法如下：

 

--例  等待 1  小时 2  分零 3  秒后才执行 SELECT  语句 waitfor delay ‟01:02:03‟ select * from employee 

 

--例  等到晚上 11  点零 8  分后才执行 SELECT  语句 waitfor time ‟23:08:00‟ select * from employee 

 

SELECT

 

语法格式如下：

select *(列名) from table_name(表名) where column_name operator value

 

select * from stock_information where stockid = str(nid)

stockname = 'str_name'

stockname like '% find this %'

stockname like '[a-zA-Z]%' ---------([]指定值的范围)

stockname like '[^F-M]%' --------- (^排除指定范围)

--------- 只能在使用 like 关键字的 where 子句中使用通配符)

or stockpath = 'stock_path'

or stocknumber < 1000

and stockindex = 24

not stock*** = 'man'

stocknumber between 20 and 100

stocknumber in(10,20,30)

order by stockid desc(asc) ---------  排序，desc-降序，asc-升序

order by 1,2 --------- by 列号

stockname = (select stockname from stock_information where stockid = 4)

---------  子查询

---------  除非能确保内层 select 只返回一个行的值，

---------  否则应在外层 where 子句中用一个 in 限定符

select distinct column_name form table_name --------- distinct 指定检索独有的列值，

不重复

select stocknumber ,"stocknumber + 10" = stocknumber + 10 from table_name

select stockname , "stocknumber" = count(*) from table_name group by stockname

---------group by  将表按行分组,指定列中有相同的值

having count(*) = 2 --------- having 选定指定的组

select *

from table1, table2

where table1.id *= table2.id --------  左外部连接，table1 中有的而 table2 中没有得

以 null 表示

table1.id =* table2.id --------  右外部连接

select stockname from table1

union [all] ----- union 合并查询结果集，all-保留重复行

select stockname from table2

insert

 

insert into table_name (Stock_name,Stock_number) value ("xxx","xxxx")

value (select Stockname , Stocknumber from Stock_table2)---value 为 select 语句

 

update

 

update table_name set Stockname = "xxx" [where Stockid = 3]

Stockname = default

Stockname = null

Stocknumber = Stockname + 4

 

delete

delete from table_name where Stockid = 3

truncate table_name -----------  删除表中所有行，仍保持表的完整性

drop table table_name ---------------  完全删除表

alter table---  修改数据库表结构

alter table database.owner.table_name add column_name char(2) null .....

sp_help table_name ----  显示表已有特征

create table table_name (name char(20), age smallint, lname varchar(30))

insert into table_name select ......... -----  实现删除列的方法（创建新表）

alter table table_name drop constraint Stockname_default ----  删除 Stockname 的

default 约束