Question

这就是问题所在，如何让用户朋友不在任何用户的朋友列表上？

这让我看到列表中的每个人：

从用户WHERE uid IN中选择uid，last_name，name，current_location （SELECT uid2 FROM friend WHERE uid1 = me（）AND uid2 IN（SELECT uid FROM friendlist_member WHERE flid IN（SELECT flid FROM friendlist WHERE owner = me（）AND type =“user_created”）））ORDER BY last_name LIMIT 0,10

但这对我没有任何帮助：

从用户WHERE uid IN中选择uid，last_name，name，current_location （SELECT uid2 FROM friend WHERE uid1 = me（）AND uid2 NOT IN（SELECT uid FROM friendlist_member WHERE flid IN（SELECT flid FROM friendlist WHERE owner = me（）AND type =“user_created”）））ORDER BY last_name LIMIT 0,10

似乎每当我包含带有“NOT IN（...）”的子句时，都会返回一个空集。

Answer 1

如果任何值NOT IN (a, b, ..., n)为NULL，则表达式a, b, ..., n将返回NULL。如果uid可以为null，请尝试向内部select中的WHERE子句添加一个额外条件以删除NULL值：

SELECT uid
FROM friendlist_member
WHERE flid IN (SELECT flid FROM friendlist WHERE owner=me() AND type = "user_created"
AND uid IS NOT NULL

查找不在任何朋友列表上的Facebook好友

1 个答案: