SQL - Group By语句

GROUP BY 子句与SELECT语句配合使用，将相同的数据分为几组。该GROUP BY子句在SELECT语句中的WHERE子句之后，并在ORDER BY子句之前。

Group By - 语法

以下代码块显示了GROUP BY子句的基本语法

SELECT column1, column2
FROM table_name
WHERE [ conditions ]
GROUP BY column1, column2
ORDER BY column1, column2

Group By - 示例

考虑CUSTOMERS表具有以下记录-

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  2 | Khilan   |  25 | Delhi     |  1500.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
|  4 | Chaitali |  25 | Mumbai    |  6500.00 |
|  5 | Hardik   |  27 | Bhopal    |  8500.00 |
|  6 | Komal    |  22 | MP        |  4500.00 |
|  7 | Learnfk    |  24 | Indore    | 10000.00 |
+----+----------+-----+-----------+----------+

如果您想知道每个客户的工资总额，那么GROUP BY查询将如下所示。

SQL> SELECT NAME, SUM(SALARY) FROM CUSTOMERS
   GROUP BY NAME;

这将产生以下输出-

+----------+-------------+
| NAME     | SUM(SALARY) |
+----------+-------------+
| Chaitali |     6500.00 |
| Hardik   |     8500.00 |
| kaushik  |     2000.00 |
| Khilan   |     1500.00 |
| Komal    |     4500.00 |
| Learnfk    |    10000.00 |
| Ramesh   |     2000.00 |
+----------+-------------+

现在，让无涯教程看一个表，其中CUSTOMERS表具有以下具有重复名称的记录-

+----+----------+-----+-----------+----------+
| ID | NAME     | AGE | ADDRESS   | SALARY   |
+----+----------+-----+-----------+----------+
|  1 | Ramesh   |  32 | Ahmedabad |  2000.00 |
|  2 | Ramesh   |  25 | Delhi     |  1500.00 |
|  3 | kaushik  |  23 | Kota      |  2000.00 |
|  4 | kaushik  |  25 | Mumbai    |  6500.00 |
|  5 | Hardik   |  27 | Bhopal    |  8500.00 |
|  6 | Komal    |  22 | MP        |  4500.00 |
|  7 | Learnfk    |  24 | Indore    | 10000.00 |
+----+----------+-----+-----------+----------+

如果您想知道每个客户的工资总额，那么GROUP BY查询将如下所示:

SQL> SELECT NAME, SUM(SALARY) FROM CUSTOMERS
   GROUP BY NAME;

这将产生以下输出-

+---------+-------------+
| NAME    | SUM(SALARY) |
+---------+-------------+
| Hardik  |     8500.00 |
| kaushik |     8500.00 |
| Komal   |     4500.00 |
| Learnfk   |    10000.00 |
| Ramesh  |     3500.00 |
+---------+-------------+