我有一个存储过程,它依赖于一个参数来启动一个订单：
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
但是……如果我这样调用这个程序：
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.
为什么它会尝试将某些东西转换为日期/时间.有人可以帮忙吗？
解决方法
问题可能是案例的类型转换.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
问题是该案例具有单个输出类型,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地方.