Question

例如：

CREATE PROCEDURE dbo.MyProc
AS
BEGIN
  SET NOCOUNT ON;
  BEGIN TRY
    ...
    DECLARE @Id INT;

    -- I don't want the following line to throw and abort processing. 
    -- I just want @Id to remain NULL. I can add a nested TRY/CATCH, but is there
    -- a better way?
    SET @Id=(SELECT Id FROM MyTable WHERE ...); 
    ...
  END TRY
  BEGIN CATCH
    ...
  END CATCH;
END;

更新：只是为了澄清，如果返回多行，我希望@Id保持为NULL。

Answer 1

我会做这样的事情来避免多行错误：

SELECT top 1 @Id = Id FROM MyTable WHERE ...

或者

SELECT @Id = Id FROM MyTable WHERE ...
if @@rowcount > 1
   set @id = null

当有多行时，最后一段将@Id设置为null。

Answer 2

试试这个：

select @id = (select max(id) from MyTable Where <YOUR CONDITION> Having count(1) = 1)

如果有多个匹配，这将返回单行，或者不返回任何行。

Answer 3

很确定这不会抛出：

SELECT @Id = Id FROM MyTable WHERE ...

有没有办法让SELECT失败而不是扔进TRY / CATCH？

3 个答案: