Question

我试图找出，如果group_concat结果中的任何数字都在一组给定的数字中。

此示例数据可用于试用：

CREATE TABLE `events` (
  `eventid` int(11) NOT NULL AUTO_INCREMENT,
  `eventname` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`eventid`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=latin1;

-- ----------------------------
--  Records of `events`
-- ----------------------------
BEGIN;
INSERT INTO `events` VALUES ('1', 'my event');
COMMIT;

-- ----------------------------
--  Table structure for `events2groups`
-- ----------------------------
CREATE TABLE `events2groups` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `eventid` int(11) DEFAULT NULL,
  `groupid` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=latin1;

-- ----------------------------
--  Records of `events2groups`
-- ----------------------------
BEGIN;
INSERT INTO `events2groups` VALUES ('1', '1', '5'), ('2', '1', '3'), ('3', '1', '1');
COMMIT;

-- ----------------------------
--  Table structure for `groups`
-- ----------------------------
CREATE TABLE `groups` (
  `groupid` int(11) NOT NULL AUTO_INCREMENT,
  `groupname` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`groupid`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;

-- ----------------------------
--  Records of `groups`
-- ----------------------------
BEGIN;
INSERT INTO `groups` VALUES ('1', 'group1'), ('2', 'group2'), ('3', 'group3'), ('4', 'group4'), ('5', 'group5');
COMMIT;

SET FOREIGN_KEY_CHECKS = 1;

然后触发此查询：

SELECT GROUP_CONCAT(groups.groupid), 
IF ( GROUP_CONCAT(groups.groupid) IN (1,2,3), 'yes', 'no' ) as isInGroup 
FROM `events`
LEFT JOIN events2groups ON events.eventid = events2groups.eventid
LEFT JOIN groups ON events2groups.groupid = groups.groupid
GROUP BY events.eventid

第一个结果列显示，该事件具有组5,3和1。用户具有组1,2和3，因此3和1匹配。我如何查询这个来从IF获得“是”？

Answer 1

为什么要使用group_concat()结果？只需使用条件聚合：

SELECT GROUP_CONCAT(groups.groupid), 
       (case when max(groups.group_id in (1, 2, 3)) > 0 then 'yes' else 'no'
        end) as isInGroup 
FROM `events` LEFT JOIN
      events2groups
      ON events.eventid = events2groups.eventid LEFT JOIN
      groups
      ON events2groups.groupid = groups.groupid
GROUP BY events.eventid;

Answer 2

SELECT GROUP_CONCAT(groups.groupid), 
  GROUP_CONCAT(case when groups.groupid IN (1,2,3) then  'yes' else 'no' end) as isInGroup 
FROM `events`
LEFT JOIN events2groups ON events.eventid = events2groups.eventid
LEFT JOIN groups ON events2groups.groupid = groups.groupid
GROUP BY events.eventid
;

结果没有，是，是

MySQL Group_concat结果给出了给定的数字

2 个答案: