Mysql Query获取表名存储在另一个表中的每个表的总和

Question

我有一个存储报告名称的MySQL表，每个条目我有一个表格，我有每个主题的标记。

Reports

+------------+----------+
|    S.No.   |ReportName|
+------------+----------+
| 1          | Report1  |
| 2          | Report2  |
+------------+----------+

Report1

+------------+----------+
|    Subject | Marks    |
+------------+----------+
| Maths      | 78       |
| English    | 99       |
+------------+----------+

Report2

+------------+----------+
|    Subject | Marks    |
+------------+----------+
| Maths      | 80       |
| English    | 99       |
+------------+----------+

现在，我希望将每个报告中的标记总和作为表格。我可以为一张桌子而不是为所有桌子做这件事。

对于一张表，它是：

SELECT (SUM(marks)) AS Total FROM `Report1`

预期：

+------------+----------+
| ReportName | Marks    |
+------------+----------+
| Report1    | 177      |
| Report2    | 179      |
+------------+----------+

Answer 1

你可以尝试一下

使用UNION合并Report1和Report2

SELECT 'Report1' AS ReportName, SUM(Marks) AS Marks
FROM Report1
UNION ALL
SELECT 'Report2' AS ReportName, SUM(Marks) AS Marks
FROM Report2

SQLFiddle

修改

表格Rport1和Rport2的数据格式相同。

我建议您可以将表格Report1和Report2合并为InfoReport

InfoReport可join Reports ReportID

+------------+----------+----------+
|    Subject | Marks    | ReportID |
+------------+----------+----------+
| Maths      | 78       |     1    |
| English    | 99       |     1    |
| Maths      | 80       |     2    |
| English    | 99       |     2    |
+------------+----------+----------+

像这样的新查询。

SELECT t1.ReportName as 'ReportName',
       SUM(T.Marks) as Marks
FROM InfoReport AS T
INNER JOIN Reports as T1 ON T.ReportID = T1.SNO
GROUP BY t1.ReportName

SQLFiddle

Answer 2

Aggregating functions in MySQL必须与group by一起使用。

在您的情况下，您需要将其添加到

SELECT (SUM(marks)) AS Total FROM `Report1`
GROUP BY whatever_column

此外，在您的示例中，您可能希望加入＆＃34;标记＆＃34;其他报告的列，因此您应该考虑使用JOIN或UNION查询。