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我只是遇到一个我不知道如何解决的问题。它与这个（已解决的）问题有关。

就像在另一篇文章中提到的那样，我有一个Media可以容纳同一用户的许多记录的表，但我只想显示最多六条记录（按顺序，无论如何，只有一张Type1 图像，然后是最多五个Type2 图像）。

只要只有一张Type图片，我现在的查询就可以正常工作，但是当我添加另一张Type图片时，查询会同时显示它们。不幸的是，像ORDER BY UserMedia.m_Type = 1 DESC LIMIT 1in an这样的东西GROUP_CONCAT不起作用，但这正是我所需要的。任何人都有一个聪明的想法如何实现这一点？

我在这里有一个带有相关代码的SQL Fiddle 。我的查询看起来像这样


SELECT
    User.u_UserName, User.u_UserMail, User.u_UserRegistration, 
        Status.us_PaymentStatus, 
        Sex.us_Gender, Sex.us_Interest, 
            Personal.up_Name, Personal.up_Dob, Personal.up_City, Personal.up_Province, 
            UserMedia.m_Id, UserMedia.m_Type, SUBSTRING_INDEX(
                GROUP_CONCAT(
                    CONCAT(
                        UserMedia.m_Type, ':', UserMedia.m_File
                    )
                    ORDER BY UserMedia.m_Type = 1, UserMedia.m_Date DESC SEPARATOR '|'
                ),'|',6
            ) AS userFiles 
FROM User AS User
    JOIN User_Status AS Status ON Status.User_u_UserId = User.u_UserId
    JOIN User_Sex_Info AS Sex ON Sex.User_u_UserId = User.u_UserId
        LEFT JOIN User_Personal_Info AS Personal ON Personal.User_u_UserId = User.u_UserId
        LEFT JOIN Media AS UserMedia ON UserMedia.User_u_UserId = User.u_UserId
WHERE User.u_UserId = '18'
    GROUP BY User.u_UserId

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1 回答 1

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去散步并提出了以下解决方案。也许不是最漂亮的，但至少它有效。我也意识到我不需要这个CONCAT功能


SELECT
    User.u_UserName, User.u_UserMail, User.u_UserRegistration, 
        Status.us_PaymentStatus, 
        Sex.us_Gender, Sex.us_Interest, 
            Personal.up_Name, Personal.up_Dob, Personal.up_City, Personal.up_Province, 
            UserMedia.m_Id, UserMedia.m_Type, SUBSTRING_INDEX(
                GROUP_CONCAT(
                    UserMedia.m_File
                        ORDER BY UserMedia.m_Type = 1 DESC 
                        SEPARATOR '|'
                ),'|',1
            ) AS userFiles, 
            SUBSTRING_INDEX(
                GROUP_CONCAT(
                    UserMedia.m_File
                        ORDER BY UserMedia.m_Date DESC 
                        SEPARATOR '|'
                ),'|',5
            ) AS userTypes, 
            SUBSTRING_INDEX(
                GROUP_CONCAT(
                    Interests.ui_Interest SEPARATOR '|'
                ),'|',5
            ) AS userInterests
FROM User AS User
    JOIN User_Status AS Status ON Status.User_u_UserId = User.u_UserId
    JOIN User_Sex_Info AS Sex ON Sex.User_u_UserId = User.u_UserId
        LEFT JOIN User_Personal_Info AS Personal ON Personal.User_u_UserId = User.u_UserId
        LEFT JOIN Media AS UserMedia ON UserMedia.User_u_UserId = User.u_UserId
        LEFT JOIN User_Interest_Info AS Interests ON Interests.User_u_UserId = User.u_UserId
WHERE User.u_UserId = :uId
    GROUP BY User.u_UserId
于 2013-07-30T14:55:13.277 回答