mysql）如何使用分组方式打印，包括当计数为0时>>

Question

当我有这样的桌子时，

<< img src =“ https://image.soinside.com/eyJ1cmwiOiAiaHR0cHM6Ly9pLnN0YWNrLmltZ3VyLmNvbS85WnBnVC5wbmcifQ==” alt =“在此处输入图像描述”>

<< img src =“ https://image.soinside.com/eyJ1cmwiOiAiaHR0cHM6Ly9pLnN0YWNrLmltZ3VyLmNvbS9Mb2NEZS5wbmcifQ==” alt =“在此处输入图像描述”>

我想获得如下图所示的select语句的结果。

<< img src =“ https://image.soinside.com/eyJ1cmwiOiAiaHR0cHM6Ly9pLnN0YWNrLmltZ3VyLmNvbS94MzZFUC5wbmcifQ==” alt =“在此处输入图像描述”>

但是，当count为0时，将省略该行。

<< img src =“ https://image.soinside.com/eyJ1cmwiOiAiaHR0cHM6Ly9pLnN0YWNrLmltZ3VyLmNvbS9XUGI5ci5wbmcifQ==” alt =“在此处输入图像描述”>

这让我感到困惑。如何修改此SQL语句以计数为0行打印？

SELECT ca.syear, COUNT(cc.joined),cc.joined
FROM schedules AS cc JOIN
     schedule_assignment AS ca
     ON ca.idx = cc.assignment
where student = 1 AND  cc.joined = 1
GROUP BY ca.syear;
[抱歉，我的声誉不到10，所以我无法立即显示图像。 ：（

[当我有这样一个表时，我想获得一个选择语句的结果，如下图所示。但是，当count为0时，将省略该行。这让我感到困惑。如何修改此SQL ...

Answer 1

我认为您只想要LEFT JOIN：