MySQL 将 "ORDER BY"子句应用于 UNION 查询

Question

ALTER PROCEDURE [dbo].[SP_GET_DDLPage]
AS
BEGIN
    SELECT NULL AS 'ID', '--None--' AS 'DSC'
    UNION
    SELECT MSP_NM AS 'ID', MSP_TITLE AS 'DSC'
    FROM MST_PAGE
    WHERE MSP_STS = ACTIVE ORDER BY MSP_NM
END

我收到一条错误消息:

MSP_NM is an invalid column

如何修复此查询并按 MSP_NM 订购？

Answer 1

我认为最好使用子查询:

SELECT *
FROM (SELECT NULL AS ID, '--None--' AS DSC
      UNION ALL
      SELECT MSP_NM AS ID, MSP_TITLE AS DSC
      FROM MST_PAGE
      WHERE MSP_STS = 'ACTIVE'
     ) t
ORDER BY ID;

您需要在 'ACTIVE' 周围加上引号，并且您可能可以在没有子查询的情况下运行查询 - 我只是认为子查询澄清了意图。