Question

我试图从同一个表格中选择两个数据集,而不是做两个问题,而是试图同时选择两个数据集。

首先,我想说:

SELECT COUNT(*) AS `total` FROM `Messages` WHERE `id` =  1 ;

第二是:

SELECT COUNT(*) AS `total_read` FROM `Messages` WHERE `id` =  1  AND `read` =  1 ;

在一个查询中是否还要这样做?

Answer 1

SELECT
    COUNT(*) total,
    SUM(IF(read= 1 ,1,0)) total_read
FROM Messages
WHERE id= 1 ;