小编Red*_*ies的帖子

SELECT users.*,(SELECT COUNT(user_id) AS mutual_connection FROM 
                (SELECT user_id 
                       FROM (
                                SELECT sender_id AS user_id 
                                FROM `connections`
                                WHERE receiver_id=users.id AND status='2' 
                                UNION 
                                SELECT receiver_id AS user_id 
                                FROM `connections` 
                                WHERE sender_id=users.id AND status='2'
                        ) tempUser
                        WHERE user_id IN (
                                  SELECT sender_id AS user_id
                                  FROM `connections` 
                                  WHERE receiver_id='4' AND status='2'
                                  UNION 
                                  SELECT receiver_id AS user_id 
                                  FROM `connections` WHERE sender_id='4' AND status='2') 
                         GROUP BY user_id) 
                as mutualConnection)

     FROM users

错误：

#1054 - 'where 子句'中的未知列'users.id'

如何使用传递值进行子查询

我想cities_extended.city_id根据加入进行更新cities

桌子 cities

CREATE TABLE `cities` (
  `id` int(11) NOT NULL,
  `city` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `state_code` char(2) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `state_id` int(11) NOT NULL DEFAULT '0'
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

ALTER TABLE `cities`
  ADD PRIMARY KEY (`id`);

桌子 cities_extended

CREATE TABLE `cities_extended` (
  `id` int(11) NOT NULL,
  `city` varchar(50) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `state_code` char(2) CHARACTER SET utf8 COLLATE utf8_unicode_ci DEFAULT NULL,
  `zip` int(5) UNSIGNED …