declare @chengji int,@sql varchar(800)
select @chengji=70
set @sql='select * from stu where 成绩='+rtrim(@chengji)--或用cast/convert
print @sql
select @chengji=70
set @sql='select * from stu where 成绩='+rtrim(@chengji)--或用cast/convert
print @sql
试试:
1.
declare @chengji int,@sql varchar(800)
select @chengji=70
set @sql='select * from stu where 成绩='+rtrim(@chengji)
print @sql2.
declare @chengji int,@sql varchar(800)
select @chengji=70
set @sql='select * from stu where 成绩='+cast(@chengji as varchar(10))
print @sql3.
declare @chengji int,@sql varchar(800)
select @chengji=70
set @sql='select * from stu where 成绩='+convert(varchar(10),@chengji)
print @sql
要用rtrim隐性转换或用cast(整数 AS NVARCHAR(100))
convert(varchar(10),@chengji)---转换后再加减
declare @chengji int,@sql varchar(800)
select @chengji=70
select * from stu where 成绩=@chengji
declare @chengji varchar(800),@sql varchar(800)
select @chengji='a'
set @sql='select * from stu where 成绩='''+@chengji+''''
print @sql--上面语句不报错是因为你只是print,并没有执行。create table stu(成绩 int)
declare @chengji varchar(800),@sql varchar(800)
select @chengji='a'
set @sql='select * from stu where 成绩='''+@chengji+''''
exec(@sql)
/*
服务器: 消息 245,级别 16,状态 1,行 1
将 varchar 值 'a' 转换为数据类型为 int 的列时发生语法错误。
*/
declare @chengji int,@sql varchar(800)
select @chengji=70
set @sql='select * from stu where 成绩=@chengji'
exec sp_executesql @sql, N'@chengji int', @chengji
rtrim(),ltrim(),rtrim(ltrim()),ltrim(rtrim()),cast(),convert
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
select @chengji='a'-- 1和4一组,5和8一组,2和3表示一个'号,6和7表示一个'号
set @sql='/*1*/select * from stu where 成绩='/*2*/'/*3*/'/*4*/+@chengji+'/*5*/'/*6*/'/*7*/'/*8*/ print @sql
set @sql='select * from stu where 成绩='''+@chengji+''''