初学 -- sql几点基础知识

1）查询某表主键

select column_name from information_schema.key_column_usage where table_name = '表名' and constraint_name like 'PK_%'

2）sql命令，像文本文件中写内容

declare @cmd sysname,@var sysname

set @var='文件的内容'

set @cmd='echo ' +@var+' >E://文件名.txt'

exec master..xp_cmdshell @cmd

3）sql事务

SET XACT_ABORT ON -- 执行失败自动回滚，用于存储过程

save tran point --保存回滚点

rollback tran point -- 回滚至回滚点

4）游标实例

declare @name varchar(20)

declare mycursor cursor

for

select categoryname from categories

open mycursor

fetch mycursor into @name

while @@fetch_status<>-1

if @@fetch_status <>-2

begin

print @name

fetch mycursor into @name

end

close mycursor

deallocate mycursor

5）sp_executesql 执行sql语句

create proc a

@tableName varchar(20),

@RowCount int output

as

declare @rowcountstring nvarchar(500)

set @rowcountstring='select @RowCount = count(*) from '+@tableName

exec sp_executesql @rowcountstring,N'@RowCount int output',@RowCount output

go

declare @count int

exec a 'products',@count output

print @count