Question

我想要做的是从表格中检索所有数据，并按用户在特定类别中播放的游戏数量进行排序。有什么办法可以使用某种“COUNT WHERE”sql语句吗？

这是我到目前为止所拥有的。如果他们在“fps”类别中玩过游戏，它只会返回用户，但是我希望它以降序显示所有用户，即使他们没有玩过fps游戏。请原谅我糟糕的桌子

SELECT user_data.user, COUNT(played_games.game_cat) as 'count'
FROM user_data, played_games
WHERE user_data.user_id = played_games.user_id and played_games.game_cat = 'fps'
GROUP BY user_data.user_id
ORDER BY 'count' DESC;

user_data table

user_id | user

1       | jeff
2       | herb
3       | dug

plays_games表

id | user_id | game | game_cat

1  |    2    | kill | fps
2  |    1    | shoot| fps
3  |    2    | COD  | fps
4  |    3    | dogs | cas

Answer 1

即使另一个表中不存在相应的记录，您也需要LEFT OUTER JOIN来获取记录。

SELECT user, coalesce(count(game_cat), 0) as count
FROM user_data LEFT OUTER JOIN played_games
ON user_data.user_id = played_games.user_id AND played_games.game_cat='fps'
GROUP BY user_data.user_id 
ORDER BY count desc;

在我的屏幕上显示以下结果

+------+-------+
| user | count |
+------+-------+
| herb |     2 |
| jeff |     1 |
| dug  |     0 |
+------+-------+

Answer 2

试试这个：

SELECT ud.user, coalesce(sum(pg.game_cat = 'fps'), 0) Total
FROM user_data ud
LEFT JOIN played_games pg ON ud.user_id = pg.user_id
GROUP BY ud.user_id
ORDER BY Total DESC

这将显示所有用户以及他们玩“fps”类别游戏的次数。

Answer 3

我就是这样做的。没有子查询，没有COALESCE，没有COUNTIF垃圾。

SELECT `users`.`user`, COUNT(`played_games`.id) AS `c`
FROM `users`
LEFT OUTER JOIN `played_games` ON
`users`.`user_id` = `played_games`.`user_id`
AND `played_games`.`game_cat` = "fps"
GROUP BY `users`.`user_id`
ORDER BY `c` DESC, `user` ASC

SQLFiddle（不确定你是否可以像这样链接他们......）

Answer 4

coalesce one很有前途，但对我不起作用，感叹〜我刚发现NULLIF是解决这个问题的好方法。记得使用LEFT JOIN

COUNT( NULLIF(TABLE.ATTR, 1) ) AS total_count

TABLE.ATTR是一些可以为NULL的字段，这是一个例子：

SELECT Posts.*, COUNT( NULLIF(Comments.user_email, 1) ) as comment_num 
FROM (`Posts`)
LEFT OUTER JOIN `Comments` ON `Comments`.`post_id` = `Posts`.`id` 
GROUP BY `Posts`.`id`
LIMIT 5

从http://www.bennadel.com/blog/579-SQL-COUNT-NULLIF-Is-Totally-Awesome.htm

得到了这个想法

Answer 5

下面查询具有用户ID和按计数排序的所有游戏类别

select * from (SELECT user_data.user, COUNT(played_games.game_cat) as 'count' 
FROM user_data, played_games 
WHERE user_data.user_id = played_games.user_id(+) GROUP BY user_data.user_id)
order by count desc

当WHERE不匹配时，在COUNT列中显示“0”？

5 个答案: