php - 如何在 mysqli 查询中应用条件

Question

我想对我的查询应用条件，就像我想将一列的值交换到另一列一样。这是我的查询，现在我不知道如何申请

mysqli_query($connect, "
    select 
        user_pro.User_No, 
        user_pro.Fist_Name, 
        user_pro.Last_Name, 
        user_pro.Designation, 
        user_pro.Profile, 
        user_pro.ProfileDP, 
        user_fndrst.Frnd_SNo, 
        user_fndrst.Rqst_Sender, 
        user_fndrst.Rqst_Receiver, 
        user_fndrst.Rqst_Status 
    from 
        user_profile INNER JOIN user_fndrst ON user_pro.User_No = user_fndrst.Rqst_Sender 
    WHERE 
        user_fndrst.Rqst_Status='1' AND 
        user_fndrst.Rqst_Receiver='$user_id' 
    ORDER BY Frnd_SNo DESC
");

这里“user_pro”表包含用户的详细信息，“user_fndrst”表包含用户的好友请求状态，$user_id 是用户的登录 ID。在这里，我希望 IF user_fndrst.Rqst_Receiver='$user_id' THEN user_fndrst.Rqst_Receiver 值更改为 user_fndrst.Rqst_Sender。

为此，我一直坚持从表“user_fndrst”中获取用户好友请求状态。

Answer 1

您的查询似乎有问题。使用这个:

SELECT 
    user_pro.User_No, user_pro.Fist_Name, user_pro.Last_Name, user_pro.Designation, user_pro.Profile, user_pro.ProfileDP, user_fndrst.Frnd_SNo, user_fndrst.Rqst_Sender, user_fndrst.Rqst_Receiver, user_fndrst.Rqst_Status 
FROM
    user_profile user_pro
    INNER JOIN user_fndrst ON user_pro.User_No = user_fndrst.Rqst_Sender 
WHERE 
    user_fndrst.Rqst_Status='1' AND user_fndrst.Rqst_Receiver='$user_id' 
ORDER BY 
    user_fndrst.Frnd_SNo DESC