sql - 设置语句在 sql 查询中的 if 子句中不起作用

Question

这是一个简单的查询，花了很多时间但我仍然无法得到这个。

我有一个问题，如果条件为真，我需要设置一个局部变量。

 Declare @asdf as nvarchar (max)
Declare @nm as nvarchar(30);
select @nm = (Select name from Core.[Lookup] where Id = 1)
Declare @dfdf as nvarchar (max)

if @nm is not null
select @asdf + 'sadf'
endif

select @nm = (Select name from Core.[Lookup] where Id = 15)
if @nm is not null
select @asdf + 'asdff'
endif

以上工作正常。但是，如果我将 select 语句更改为 set 语句，则会出现错误。'endif' 附近的语法不正确。

Declare @asdf as nvarchar (max)
Declare @nm as nvarchar(30);
select @nm = (Select name from Core.[Lookup] where Id = 1)
Declare @dfdf as nvarchar (max)

if @nm is not null
set @asdf = 'sadf'
endif

select @nm = (Select name from Core.[Lookup] where Id = 15)
if @nm is not null
set @asdf = 'asdff'
endif

谢谢

Answer 1

中没有endif关键字T-SQL，正确的查询如下所示：

Declare @asdf as nvarchar (max)
Declare @nm as nvarchar(30);
select @nm = (Select name from Core.[Lookup] where Id = 1)
Declare @dfdf as nvarchar (max)

if @nm is not null
begin
     set @asdf = 'sadf'
end

select @nm = (Select name from Core.[Lookup] where Id = 15)
if @nm is not null
begin
   set @asdf = 'asdff'
end