Question

尝试检查插入的表列level_name中输入的值是否与Levels表列level_name匹配。我的查询返回错误Subquery returned more than 1 value.。试着按照Dan Guzman的那个编写代码。

Declare @levelname nvarchar(MAX)= 
( 
 SELECT [LEVEL_NAME] + ' '
 FROM inserted 
 WHERE (select LEVEL_NAME from levels where level_name=(select level_name 
 from  inserted)) IS NULL 
 FOR XML PATH('') 
); 
if @levelname is not null 
BEGIN 
  RAISERROR(); 
END

Answer 1

我建议您在查询中使用Top 1或使用以下格式：

IF Exists(SELECT  [LEVEL_NAME]
          FROM inserted i
          INNER JOIN levels l ON l.Level_name = i.Level_name) Begin
  RAISERROR('Your error message',16,1); 
END

OR

IF (SELECT  COUNT(*)
    FROM inserted i
    INNER JOIN levels l ON l.Level_name = i.Level_name)=0 Begin
  RAISERROR('Your error message',16,1); 
END

我建议在level_name列上使用UNIQUE INDEX。为了限制用户插入duplication level_name值。

Answer 2

试试这个：

DECLARE @levelname NVARCHAR(MAX)= 
( 
 SELECT [LEVEL_NAME] + ' '
 FROM   inserted 
 WHERE  EXISTS (SELECT LEVEL_NAME FROM levels
                    WHERE  level_name IN (SELECT level_name FROM inserted))
 FOR XML PATH('') 
); 
IF @levelname IS NOT NULL 
BEGIN 
  RAISERROR(); 
END

插入触发器问题，子查询返回超过1行

2 个答案: