mysql - Sql 按组选择所有对话

Question

在按摩系统中，我想选择用户的所有对话。

我的 msg 表如下:

id  | mfrom | mto  | date
=========================
1   | 10    | 12   | 0000
2   | 14    | 10   | 0000
3   | 10    | 14   | 0000
4   | 16    | 10   | 0000
5   | 10    | 16   | 0000

这里我的用户 ID 为:10。如上所述，我与用户 ID 12、14、16 进行了 3 次对话

我使用此 SQL 来获取与我对话的用户 ID:

$results = mysqli_query($db,"SELECT mfrom FROM msg WHERE `mto`='10' GROUP BY `mfrom` ORDER BY `date` DESC");
while($rows = mysqli_fetch_assoc($results)) {
    $mfroms[] = $rows['mfrom'];
}

$results = mysqli_query($db,"SELECT mto FROM msg WHERE `mfrom`='10' GROUP BY `mto` ORDER BY `date` DESC");
while($rows = mysqli_fetch_assoc($results)) {
    $mtos[] = $rows['mto'];
}

$result = array_unique(array_merge($mfroms,$mtos), SORT_REGULAR);

上面的查询给了我一个数组结果 12,14,16

现在我的问题是，我无法按组获取与我的所有对话。这意味着，我想从上表中得到如下结果:

user 12 conversation with user 10(me) total 1 display recent massage only
-------------------------------------------------------------------------
user 14 conversation with user 10(me) total 2 display recent massage only
-------------------------------------------------------------------------
user 16 conversation with user 10(me) total 2 display recent massage only

Answer 1

将 AccountTable 替换为您的表名称，将 10 替换为您的用户 ID 并进行测试。

SELECT s.user1,s.user2,count(*) as recent_messages
FROM (
    SELECT CASE WHEN t.mfrom > t.mto THEN t.mfrom ELSE t.mto END as user1,
           CASE WHEN t.mfrom < t.mto THEN t.mfrom ELSE t.mto END as user2
    FROM AccountTable t WHERE t.mfrom = 10 OR t.mto=10) s
GROUP BY s.user1,s.user2