mysql - MySQL：多个 SUMS 计数组合值 WHERE 条件

Question

article_vote table
+------------+------+
| article_id | vote |
+------------+------+
|          1 |    3 |
|          1 |    1 |
|          1 |   -1 |
|          1 |   -2 |
+------------+------+

在 MySQL 5.5 中，我一直试图从上表中返回两个结果。1. 所有反对票的总和。2. 所有正票的总和。所以正数应该是4负数应该是-3。投票字段没有 NULL 值。

此 SQL 不能按我的意图工作：

SELECT vote,
    SUM(vote > 0) AS positive,
    SUM(vote < 1) AS negative
FROM article_vote
WHERE vote_article_id = 50
GROUP BY vote

当我在上面的数据集上使用它时，它返回：

Array ( [vote] => -22 [positive] => 0 [negative] => 1 ) 

我哪里错了？

Answer 1

试试这个：

SELECT
    SUM(if(vote > 0, vote, 0)) positive,
    SUM(if(vote < 0, vote, 0)) negative
FROM article_vote
WHERE article_id = 1

结果：

| POSITIVE | NEGATIVE |
|----------|----------|
|        4 |       -3 |

在这里拉小提琴。

Answer 2

mysql> SELECT * FROM article_vote;
+------------+------+
| article_id | vote |
+------------+------+
|          1 |    3 |
|          1 |    1 |
|          1 |   -1 |
|          1 |   -2 |
+------------+------+
4 rows in set (0.00 sec)

SELECT 
    SUM(CASE WHEN vote > 0 THEN vote ELSE 0 END) AS positive,
    SUM(CASE WHEN vote < 0 THEN vote ELSE 0 END) AS negative
FROM article_vote
WHERE article_id = 1;

+----------+----------+
| positive | negative |
+----------+----------+
|        4 |       -3 |
+----------+----------+

http://sqlfiddle.com/#!2/c18e3/1

Answer 3

纠正这样的事情：

select article_id, 
  sum(case when vote >0 then vote else 0 end) as postive,
  sum(case when vote <0 then vote else 0 end) as negative
FROM article_vote
GROUP BY article_id

不确定您的位置条件，对不起。

Answer 4

你可以尝试这样的事情：

SELECT article_id,

    (SELECT SUM(vote) 
     FROM article_vote 
     WHERE vote > 0 
     AND article_id = 50) AS positive,

    (SELECT SUM(vote)
     FROM article_vote
     WHERE vote < 0
     AND article_id = 50) AS negative

FROM article_vote
WHERE article_id = 50
GROUP BY article_id