Ajax请求不是异步的(Ajax request are not async)

 您可以使用UNION执行两个查询，其中一个查询直接在PNUM上匹配GROUP <> 1值，另一个匹配PNUM并通过group_members连接GROUP = 1值。 
 
 在第二部分中，您需要连接两次以使users获得与原始PNUM匹配的组成员。 
 
 由于GROUP条件各自相反，因此只有UNION一部分会返回结果。 
 
/* First part of UNION directly matches PNUM for GROUP = 0 */
SELECT dloc
FROM users
WHERE 
  PNUM = 23101
  AND `group` <> 1
UNION
/**
 Second part of UNION matches GROUP = 1
 and joins through group_members back to users
 to get member dloc (from the second users join)
 */
SELECT uu.dloc
FROM users u
   INNER JOIN group_members m ON u.`GROUP` = 1 AND u.id = m.group_id
   INNER JOIN users uu ON m.member_id = uu.id
WHERE 
   u.PNUM = 23101
 
 不幸的是，这需要在查询中放置两次PNUM值，每个UNION部分一次，但这并不是那么糟糕。 
 
 它在这里 （使用MySQL而不是SQLite，但这并不重要） 
 
 使用OR和IN()子查询的原始方法，也可以完成，但我为GROUP = 0和GROUP = 1添加了WHERE条件。 
 
SELECT users.dloc 
FROM users 
WHERE users.id in (
    SELECT group_members.member_id 
    FROM group_members 
      INNER JOIN users on users.id = group_members.group_id 
    WHERE users.pnum='23101' AND `GROUP` = 1
 )
 OR users.id IN (
    SELECT users.ID
    FROM users 
    WHERE pnum='23101' AND `GROUP` = 0
);
 
 这是替代方法...... 

You may use a UNION to execute both queries, one of which matches directly on PNUM for values where GROUP <> 1 and the other which matches on PNUM and joins through group_members for values where GROUP = 1.
 
In the second part, you need to join twice to users to get the members of the group matching the original PNUM.
 
Since the GROUP condition is opposite in each, only one part of the UNION will ever return results. 
 
/* First part of UNION directly matches PNUM for GROUP = 0 */
SELECT dloc
FROM users
WHERE 
  PNUM = 23101
  AND `group` <> 1
UNION
/**
 Second part of UNION matches GROUP = 1
 and joins through group_members back to users
 to get member dloc (from the second users join)
 */
SELECT uu.dloc
FROM users u
   INNER JOIN group_members m ON u.`GROUP` = 1 AND u.id = m.group_id
   INNER JOIN users uu ON m.member_id = uu.id
WHERE 
   u.PNUM = 23101
 
This does unfortunately require placing the PNUM value twice in the query, once per UNION part, but that isn't so bad.
 
Here it is in action (using MySQL rather than SQLite, but that doesn't really matter)
 
Using your original method with OR and an IN() subquery, it can also be done, but I've added WHERE conditions for GROUP = 0 and GROUP = 1.
 
SELECT users.dloc 
FROM users 
WHERE users.id in (
    SELECT group_members.member_id 
    FROM group_members 
      INNER JOIN users on users.id = group_members.group_id 
    WHERE users.pnum='23101' AND `GROUP` = 1
 )
 OR users.id IN (
    SELECT users.ID
    FROM users 
    WHERE pnum='23101' AND `GROUP` = 0
);
 
And here's the alternative method in action...