sql
如何取一个变量值的前几位字符,例如insert into #t
exec('select substring('+@tbname2+',1,8),SUM(rmbchange),(select SUM(rmbchange) from [dbo].['+@tbname2+'] where rmbchange>0) from [dbo].['+@tbname2+'] where rmbchange<0'),这个语句的substring('+@tbname2+',1,8)这样写对吗还是substring(‘'+@tbname2+’',1,8)两个引号?