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How can we use group function with non-group fields in MySQL SELECT query?

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2023-09-10 17:41:02476browse

我们如何在 MySQL SELECT 查询中将组函数与非组字段一起使用?

If we want to use grouping function on non-grouped fields in SELECT query, we must use GROUP BY clause. The general syntax can be as follows

Syntax

SELECT group_function1,…, non-group-column1,… from table_name GROUP BY column_name;

Example

mysql> Select COUNT(*), id from Student GROUP BY id;
+----------+------+
| COUNT(*) | id   |
+----------+------+
| 1        | 1    |
| 1        | 2    |
| 1        | 15   |
| 1        | 17   |
| 1        | 20   |
+----------+------+
5 rows in set (0.00 sec)

mysql> Select COUNT(*), address from Student GROUP BY id;
+----------+---------+
| COUNT(*) | address |
+----------+---------+
| 1        | Delhi   |
| 1        | Mumbai  |
| 1        | Delhi   |
| 1        | Shimla  |
| 1        | Jaipur  |
+----------+---------+
5 rows in set (0.00 sec)

The fields after the GROUP BY clause can be different from the non-group fields given in the SELECT query.

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