子查询返回值不止一个

Question

**这个触发器执行过程中出现了子查询返回值不止一个的问题 **
应该怎么解决呢？

ALTER TRIGGER [dbo].[limit_buy] ON [dbo].[ord]
AFTER INSERT 
AS
BEGIN
DECLARE @lim INT;
DECLARE @num INT
DECLARE @id INT 
SET @lim=(SELECT d_stock FROM dish,ord WHERE ord.o_did=dish.d_id);
SET @num=(SELECT o_num FROM INSERTED)
SET @id=(SELECT o_did FROM INSERTED)
if (@lim is NOT NULL AND @num>@lim) 
UPDATE ord SET o_num=@lim WHERE o_did=@id
END

Answer 1

SET @lim=(SELECT d_stock FROM dish,ord WHERE ord.o_did=dish.d_id);
设置更多条件或者处理表内数据，确保语句返回一个d_stock值，保证 update 语句set o_num=一个值。
SET @id=(SELECT o_did FROM INSERTED)
设置更多条件或者处理表内数据，确保语句返回一个 o_did值。保证 where条件 o_did=一个值 。