使用mysql在一个查询中查询计数，总和，条件

Question

我在mysql数据库中有这个表：

TABLE rating
| id         (int, primary)
| id_company (int, index)
| state      (enum: 'waiting','done','refuse')
| rating     (int between 1 and 5)

我想获取一个id_company的统计信息：

• 数字行
• 状态=已完成的数字行
• 总和评级
• 与州=完成的总和评级

为此我有2个查询（例如id_company = 2）：

SELECT COUNT(1) as `nbr`, SUM(`rating`) as `total` FROM `rating` WHERE `id_company`=2
SELECT COUNT(1) as `nbr`, SUM(`rating`) as `total` FROM `rating` WHERE `id_company`=2 AND `state`='done'

但是可以创建一个唯一的查询来获取此统计信息吗？

Answer 1

您可以尝试这样的事情：

SELECT COUNT(*) as `nbr1`, 
       SUM(`rating`) as `total1`,
       SUM(`state`='done') as `nbr2`, 
       SUM(CASE 
              WHEN `state`='done' THEN `rating` 
              ELSE 0 
           END) as `total2`  
FROM `rating` 
WHERE `id_company`=2