我有一个存储过程,它通过依赖参数来启动订单:
DROP PROCEDURE [dbo].[GetUsersByClusterAndUserName]
GO
CREATE PROCEDURE [dbo].[GetUsersByClusterAndUserName]
@SortField [nvarchar] (256) = 'UserName',
@SortOrder [int] = 0
AS
SELECT * FROM [User]
ORDER BY
CASE WHEN @SortOrder = 0 THEN
CASE
WHEN @SortField = 'UserName' THEN User_UserName
WHEN @SortField = 'LastLoginDate' THEN User_LastLoginDate
WHEN @SortField = 'CreationDate' THEN User_CreationDate END
END ASC,
CASE WHEN @SortOrder = 1 THEN
CASE
WHEN @SortField = 'UserName' THEN User_UserName
WHEN @SortField = 'LastLoginDate' THEN User_LastLoginDate
WHEN @SortField = 'CreationDate' THEN [User_CreationDate] END
END DESC
RETURN 0
GO
然而......如果我按照这样的程序调用:
EXEC dbo.GetUsersByClusterAndUserName @SortOrder=1, @SortField='UserName'
我收到以下错误:
Msg 241, Level 16, State 1, Procedure GetUsersByClusterAndUserName, Line 7
Conversion failed when converting date and/or time from character string.
为什么会尝试将某些内容转换为日期/时间。有人可以帮忙吗?
答案 0 :(得分:4)
问题可能是来自case
的类型转换。以这种方式使用order by
时,请使用多个case
语句:
ORDER BY (CASE WHEN @SortOrder = 0 AND @SortField = 'UserName' THEN User_UserName END),
(CASE WHEN @SortOrder = 0 AND @SortField = 'User_LastLoginDate' THEN User_LastLoginDate END),
(CASE WHEN @SortOrder = 0 AND @SortField = 'User_CreationDate' THEN User_CreationDate END),
(CASE WHEN @SortOrder = 1 AND @SortField = 'UserName' THEN User_UserName END) DESC,
(CASE WHEN @SortOrder = 1 AND @SortField = 'User_LastLoginDate' THEN User_LastLoginDate END) DESC,
(CASE WHEN @SortOrder = 1 AND @SortField = 'User_CreationDate' THEN User_CreationDate END) DESC
问题是case
有一个输出类型,在编译查询时确定。此类型基于逻辑组合THEN
子句的所有类型。因此,每个then
子句的结果将转换为整体类型 - 这就是您的错误发生的位置。
您可以阅读有关数据优先级规则here的信息。但解决方案很简单:使用多个case
语句。