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declare @i int
declare @v_n varchar(100) ,@fname varchar(100)
declare @str1 varchar(500)
set @i = 1
while @i <= 10
begin
@fname = 'column1' + cast(@i as varchar)
set @str1='update a set '+@fname
+' = b.total
from dm a , dn b
where a.yyear=b.yyear and a.mmonth=1 '
exec (@str1)
end
declare @i int
declare @v_n varchar(100) ,@fname varchar(100)
set @i = 1
while @i <= 10
begin
set @fname = 'column1' + cast(@i as varchar)
exec ('update a
set a.'+@fname+' = b.total
from dm a , dn b
where a.yyear=b.yyear and a.mmonth=1 ')
set @i=@i+1
end
declare @i int
declare @v_n varchar(100) ,@fname varchar(100)
set @i = 1
while @i <= 10
begin
set @fname = 'column1' + cast(@i as varchar)
exec ('update a
a.'+@fname+' = b.total
from dm a , dn b
where a.yyear=b.yyear and a.mmonth=1 ')
set @i=@i+1
end
动态sql语句基本语法
1 :普通SQL语句可以用Exec执行
eg: Select * from tableName
Exec('select * from tableName')
Exec sp_executesql N'select * from tableName' -- 请注意字符串前一定要加N
2:字段名,表名,数据库名之类作为变量时,必须用动态SQL
eg:
declare @fname varchar(20)
set @fname = 'FiledName'
Select @fname from tableName -- 错误,不会提示错误,但结果为固定值FiledName,并非所要。
Exec('select ' + @fname + ' from tableName') -- 请注意 加号前后的 单引号的边上加空格
当然将字符串改成变量的形式也可
declare @fname varchar(20)
set @fname = 'FiledName' --设置字段名
declare @s varchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句会报错
declare @s Nvarchar(1000) -- 注意此处改为nvarchar(1000)
set @s = 'select ' + @fname + ' from tableName'
Exec(@s) -- 成功
exec sp_executesql @s -- 此句正确
3. 输出参数
declare @num int,
@sqls nvarchar(4000)
set @sqls='select count(*) from tableName'
exec(@sqls)
--如何将exec执行结果放入变量中?
declare @num int,
@sqls nvarchar(4000)
set @sqls='select @a=count(*) from tableName '
exec sp_executesql @sqls,N'@a int output',@num output
select @num
--要使用动态SQL.
declare @i int
declare @v_n varchar(100)
declare @fname varchar(100)
declare @sql as varchar(100)
set @i = 1
while @i <= 10
begin
@fname = 'column1' + cast(@i as varchar)
set @sql = 'update a set ' + @fname + ' = b.total from dm a dn b where a.yyear=b.yyear and a.mmonth=1'
exec(@sql)
set @i = @i + 1
end