MYSQL - 如何让3行数据成为1行数据

Question

现在我联合3表并选择下面显示。

|remark|totalA|totalB|tatalC|
-----------------------------
|   a  | 123  | NULL | NULL |

|   a  | NULL | 123  | NULL |

|   a  | NULL | NULL | 123  |

如何让它成为如下所示的1行？

|remark|totalA|totalB|tatalC|
-----------------------------
|   a  | 123  | 123  | 123  |

我尝试分组并将其区分开，但它显示在下面

|remark|totalA|totalB|tatalC|
-----------------------------
|   a  | 123  | NULL | NULL |

Answer 1

select 
   remark,
   sum(totalA) as totalA,
   sum(totalB) as totalB,
   sum(totalC) as totalC
from the_table
group by remark

Answer 2

将sum与group by一起使用

select remark, sum(totalA), sum(totalB), sum(totalC)
from table_name
group by remark

Answer 3

使用聚合函数，如MIN()，默认情况下将排除空值：

SELECT remark, MIN(totalA), MIN(totalB), MIN(totalC)
FROM Remarks
GROUP BY remark