Question

$data['do'] = $this->db->query("SELECT MONTH(`date`) as month, COUNT(*) as count
FROM `simple` WHERE `ochistka` = 'somevalue' GROUP BY MONTH(`date`)");

这里我选择的是每个月都有一些值的字段，但我如何选择另一个字段与其他条件，而不是计数（）作为计数，而是另外一个计数（）作为count2，有其他WHERE子句可能吗？

Answer 1

如果我理解你正在尝试实现的目标，你可以使用SUM（IF）技巧，如下所示：

SELECT MONTH(`date`) as month,
       SUM(IF(`ochistka` = 'somevalue', 1, 0)) as count1,
       SUM(IF(`ochistka` = 'othervalue', 1, 0)) as count2
FROM `simple`
GROUP BY MONTH(`date`)

Answer 2

目前无法测试代码，但基本思路是使用子查询：

SELECT t1.month as month, t1.count as count1, t2.count as count2 
FROM
    (SELECT MONTH(`date`) as month, COUNT(*) as count
     FROM `simple` 
     WHERE `ochistka` = 'somevalue' 
     GROUP BY MONTH(`date`)) AS t1
INNER JOIN
    (SELECT MONTH(`date`) as month, COUNT(*) as count 
     FROM `simple` 
     WHERE `ochistka` = 'someothervalue' 
     GROUP BY MONTH(`date`)) AS t2 ON t1.month = t2.month

如何制作不同的WHERE子句

2 个答案: