伙计们,我想合并两个表。第一个表是comments
,第二个表是likes
。喜欢包含喜欢和不喜欢col rate
(1=喜欢,2=不喜欢)
所以我想当我显示所有评论时,我还想添加两个新的列likes
和dislikes
,其中我计算有多少喜欢和不喜欢有一个评论。我这样做只是为了喜欢,但我不知道怎么做也是为了不喜欢。
所以这里有一张我保存点赞的表格:
like_id item_id account_id rate time host
------- ------- ---------- ------ ------------------- --------
308 262 1 1 2016-03-18 13:45:16 (NULL)
309 263 1 2 2016-03-18 13:45:33 (NULL)
310 262 7 2 2016-03-18 14:23:49 (NULL)
311 262 8 1 2016-03-18 14:24:11 (NULL)
下面是评论表:
comment_id item_id content account_id time
------- ------- ---------- ------------ -------------------
308 262 Test comment 1 2016-03-18 13:45:16
所以我想做这个结果
comment_id item_id content account_id time Likes Dislike
------- ------- --------- ------------ ----- -------- ------
1 267 test comm 1 4 2
我的查询
SELECT c.comment_id, acc.account_id, acc.account_firstname, acc.account_lastname,p.photo_name,p.photo_guid, COUNT(_like.item_id) AS likes
FROM pb_account_comments AS c
INNER JOIN pb_accounts AS acc ON acc.account_id = c.account_id
LEFT JOIN pb_account_photos AS p ON p.photo_id = acc.profile_picture_id
LEFT JOIN pb_account_likes AS _like ON _like.item_id = c.comment_id
WHERE c.item_id = '2' GROUP BY c.comment_id
ORDER BY posted_date ASC LIMIT 0,3;
我的查询只计算点赞,这很好,但我怎么能计算和不喜欢呢?
我不确定额外的列需要什么。通常情况下,此类列也应包含在GROUP BY
中。
一个更简单的查询版本只是使用条件聚合返回每个注释的信息:
SELECT c.comment_id,
COALESCE(SUM(l.rate = 1), 0) AS likes,
COALESCE(SUM(l.rate = 2), 0) AS dislikes
FROM pb_account_comments c INNER JOIN
pb_account_likes l
ON l.item_id = c.comment_id
WHERE c.item_id = 2
GROUP BY c.comment_id
ORDER BY posted_date ASC
LIMIT 0, 3;