Question

没有设法找到问题的答案。因此，决定在这里分享。希望它能帮助任何人和专业人士分享更有效的解决方案

我在MSSQL中创建了一个函数，它接受一个参数并尝试在映射表中查找相应的记录。映射记录的提取是使用＆＃39; With子句＆＃39;：

实现的

CREATE FUNCTION [dbo].[GetMappedValue]
(
    @field nvarchar(50) = null
)
RETURNS VARCHAR(50)
AS 
BEGIN
    ;WITH active_mappings AS 
        (SELECT map_key, map_value, ROW_NUMBER() OVER (PARTITION BY map_key ORDER BY updated DESC) AS n
                FROM MappingTable WHERE tag = 'Active')

    RETURN SELECT TOP 1 map_value FROM active_mappings 
           WHERE n=1 AND map_key = @field
END
GO

但是出于一个奇怪的原因：标量值函数中的RETURN语句必须包含一个参数＆＃39;发生错误

Answer 1

为了解决这个问题，我必须声明一个变量并将select的结果赋值给变量，然后才返回它：

CREATE FUNCTION [dbo].[GetMappedValue]
(
    @field nvarchar(50) = null
)
RETURNS VARCHAR(50)
AS 
BEGIN
    Declare @result nvarchar(50)
    ;WITH active_mappings AS 
        (SELECT map_key, map_value, ROW_NUMBER() OVER (PARTITION BY map_key ORDER BY updated DESC) AS n
                FROM MappingTable WHERE tag = 'Active')

    SELECT @Result = (SELECT TOP 1 map_value FROM active_mappings 
           WHERE n=1 AND map_key = @field)

     RETURN @Result
END
GO

标量值函数中的RETURN语句必须包含参数

1 个答案: