311 lines
6.1 KiB
Markdown
Executable File
311 lines
6.1 KiB
Markdown
Executable File
一、定义变量
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--简单赋值
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```sql
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declare @a int
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set @a=5
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print @a --使用select语句赋值
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declare @user1 nvarchar(50)
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select @user1='张三'
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print @user1
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declare @user2 nvarchar(50)
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select @user2 = Name from ST_User where ID=1
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print @user2 --使用update语句赋值
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declare @user3 nvarchar(50)
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update ST_User set @user3 = Name where ID=1
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print @user3
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```
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二、表、临时表、表变量
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--创建临时表1
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```sql
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create table #DU_User1
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```
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(
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[ID] [int] NOT NULL,
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[Oid] [int] NOT NULL,
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[Login] [nvarchar](50) NOT NULL,
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[Rtx] [nvarchar](4) NOT NULL,
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[Name] [nvarchar](5) NOT NULL,
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[Password] [nvarchar](max) NULL,
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[State] [nvarchar](8) NOT NULL
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);
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--向临时表1插入一条记录
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```sql
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insert into #DU_User1 (ID,Oid,[Login],Rtx,Name,[Password],State) values (100,2,'LS','0000','临时','321','特殊'); --从ST_User查询数据，填充至新生成的临时表
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select * into #DU_User2 from ST_User where ID<8 --查询并联合两临时表
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select * from #DU_User2 where ID<3 union select * from #DU_User1 --删除两临时表
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drop table #DU_User1
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drop table #DU_User2 --创建临时表
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CREATE TABLE #t
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```
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(
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[ID] [int] NOT NULL,
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[Oid] [int] NOT NULL,
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[Login] [nvarchar](50) NOT NULL,
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[Rtx] [nvarchar](4) NOT NULL,
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[Name] [nvarchar](5) NOT NULL,
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[Password] [nvarchar](max) NULL,
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[State] [nvarchar](8) NOT NULL,
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) --将查询结果集（多条数据）插入临时表
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```sql
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insert into #t select * from ST_User
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```
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--不能这样插入
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--select * into #t from dbo.ST_User --添加一列，为int型自增长子段
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```sql
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alter table #t add [myid] int NOT NULL IDENTITY(1,1)
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```
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--添加一列，默认填充全球唯一标识
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```sql
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alter table #t add [myid1] uniqueidentifier NOT NULL default(newid()) select * from #t
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drop table #t
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```
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--给查询结果集增加自增长列 --无主键时：
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```sql
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select IDENTITY(int,1,1)as ID, Name,[Login],[Password] into #t from ST_User
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select * from #t --有主键时：
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select (select SUM(1) from ST_User where ID<= a.ID) as myID,* from ST_User a order by myID
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```
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--定义表变量
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```sql
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declare @t table
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```
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(
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id int not null,
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msg nvarchar(50) null
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)
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```sql
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insert into @t values(1,'1')
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insert into @t values(2,'2')
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select * from @t
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```
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三、循环
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--while循环计算1到100的和
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```sql
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declare @a int
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declare @sum int
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set @a=1
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set @sum=0
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while @a<=100
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```
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begin
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```sql
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set @sum+=@a
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set @a+=1
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```
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end
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print @sum
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四、条件语句
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--if,else条件分支
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if(1+1=2)
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begin
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print '对'
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end
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else
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begin
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print '错'
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```sql
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end --when then条件分支
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declare @today int
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declare @week nvarchar(3)
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set @today=3
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set @week=case
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```
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when @today=1 then '星期一'
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when @today=2 then '星期二'
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when @today=3 then '星期三'
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when @today=4 then '星期四'
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when @today=5 then '星期五'
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when @today=6 then '星期六'
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when @today=7 then '星期日'
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else '值错误'
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end
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```sql
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print @week
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```
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五、游标
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```sql
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declare @ID int
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declare @Oid int
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declare @Login varchar(50) --定义一个游标
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declare user_cur cursor for select ID,Oid,[Login] from ST_User
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```
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--打开游标
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```sql
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open user_cur
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while @@fetch_status=0
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```
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begin
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--读取游标
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```sql
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fetch next from user_cur into @ID,@Oid,@Login
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print @ID
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```
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--print @Login
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end
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close user_cur
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--摧毁游标
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deallocate user_cur
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六、触发器
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触发器中的临时表：
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Inserted
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存放进行insert和update 操作后的数据
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Deleted
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存放进行delete 和update操作前的数据
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--创建触发器
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```sql
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Create trigger User_OnUpdate
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```
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On ST_User
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for Update
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As
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```sql
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declare @msg nvarchar(50)
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```
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--@msg记录修改情况
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```sql
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select @msg = N'姓名从“' + Deleted.Name + N'”修改为“' + Inserted.Name + '”' from Inserted,Deleted
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```
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--插入日志表
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```sql
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insert into [LOG](MSG)values(@msg) --删除触发器
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drop trigger User_OnUpdate
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```
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七、存储过程
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--创建带output参数的存储过程
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```sql
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CREATE PROCEDURE PR_Sum
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```
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@a int,
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@b int,
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@sum int output
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AS
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BEGIN
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```sql
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set @sum=@a+@b
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END --创建Return返回值存储过程
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CREATE PROCEDURE PR_Sum2
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```
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@a int,
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@b int
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AS
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BEGIN
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Return @a+@b
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```sql
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END --执行存储过程获取output型返回值
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declare @mysum int
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execute PR_Sum 1,2,@mysum output
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print @mysum --执行存储过程获取Return型返回值
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declare @mysum2 int
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execute @mysum2= PR_Sum2 1,2
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print @mysum2
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```
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八、自定义函数
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函数的分类：
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1）标量值函数
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2）表值函数
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a:内联表值函数
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b:多语句表值函数
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3）系统函数
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--新建标量值函数
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```sql
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create function FUNC_Sum1
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```
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(
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@a int,
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@b int
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)
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returns int
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as
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begin
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return @a+@b
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```sql
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end --新建内联表值函数
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create function FUNC_UserTab_1
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```
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(
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@myId int
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)
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returns table
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as
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return (select * from ST_User where ID<@myId) --新建多语句表值函数
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```sql
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create function FUNC_UserTab_2
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```
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(
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@myId int
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)
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returns @t table
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(
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[ID] [int] NOT NULL,
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[Oid] [int] NOT NULL,
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[Login] [nvarchar](50) NOT NULL,
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[Rtx] [nvarchar](4) NOT NULL,
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[Name] [nvarchar](5) NOT NULL,
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[Password] [nvarchar](max) NULL,
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[State] [nvarchar](8) NOT NULL
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)
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as
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begin
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```sql
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insert into @t select * from ST_User where ID<@myId
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```
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return
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```sql
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end --调用表值函数
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select * from dbo.FUNC_UserTab_1(15)
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```
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--调用标量值函数
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```sql
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declare @s int
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set @s=dbo.FUNC_Sum1(100,50)
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print @s --删除标量值函数
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drop function FUNC_Sum1
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```
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谈谈自定义函数与存储过程的区别：
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一、自定义函数：
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1. 可以返回表变量
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2. 限制颇多，包括
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不能使用output参数；
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不能用临时表；
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函数内部的操作不能影响到外部环境；
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不能通过select返回结果集；
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不能update，delete，数据库表；
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3. 必须return 一个标量值或表变量
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自定义函数一般用在复用度高，功能简单单一，争对性强的地方。
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二、存储过程
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1. 不能返回表变量
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2. 限制少，可以执行对数据库表的操作，可以返回数据集
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3. 可以return一个标量值，也可以省略return
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存储过程一般用在实现复杂的功能，数据操纵方面。 |