Question

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

在这里，我选择了每个月都有值的字段，但我如何选择另一个有其他条件的字段，不是像count（）那样的count，而是像count2那样的count（），有其他WHERE子句，这是可能的吗？

Answer 1

如果我正确理解了你想要实现的目标，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

现在无法测试代码，但基本思想是使用子查询：

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

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