sql-server - 如果结果为 0，如何在存储过程上启动 THROW？

Question

我想知道如果有 0 个结果，我必须怎么做才能在以下存储过程中引发异常，以便它可以选择 NULL 行？这是针对 MSSQL 的，非常感谢。

...

BEGIN TRY
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;

    SELECT
        NoteId,
        Url,
        Subject,
        Content,
        ExpiresAt,
        RemindAt
    FROM dbo.browsingnotes_Notes
    WHERE UserId = @UserId
        AND Hash = @Hash
END TRY
BEGIN CATCH
    SELECT
        NULL AS 'NoteId',
        NULL AS 'Url',
        NULL AS 'Subject',
        NULL AS 'Content',
        NULL AS 'ExpiresAt',
        NULL AS 'RemindAt'
END CATCH

Answer 1

RAISERROR行得通吗？或者，正如@Candie 所说，THROW在 SQL 2012 中

您可以@@RowCount在第一次选择后检查，如果为 0，则选择第二次。

Answer 2

你可以阅读这篇文章

THROW [ { error_number | @local_variable },
        { message | @local_variable },
    { state | @local_variable }
] [ ; ]

链接：http: //msdn.microsoft.com/fr-fr/library/ee677615.aspx

Answer 3

UNION如果没有其他行，您可以简单地在结果集中添加一个 NULL 行：

SELECT
    NoteId, 
    Url, 
    Subject, 
    Content, 
    ExpiresAt, 
    RemindAt 
FROM dbo.browsingnotes_Notes 
WHERE UserId = @UserId 
    AND Hash = @Hash 
union
select NULL, NULL, NULL, NULL, NULL, NULL
  where not exists ( select 42 from dbo.browsingnotes_Notes where UserId = @UserId and Hash = @Hash )