MySQL 如何在选择查询中按正数或负数值进行GROUP BY

以下是在选择查询中按正数或负数值进行GROUP BY的语法：

select *from yourTableName group by -yourColumnName;

让我们首先创建一个表：

mysql> create table DemoTable (Value int);
Query OK, 0 rows affected (0.60 sec)

以下是使用insert命令向表中插入一些记录的查询：

mysql> insert into DemoTable values(-10);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values(-20);
Query OK, 1 row affected (0.10 sec)
mysql> insert into DemoTable values(20);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.13 sec)
mysql> insert into DemoTable values(-10);
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable values(-10);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable values(-20);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(-30);
Query OK, 1 row affected (0.07 sec)
mysql> insert into DemoTable values(30);
Query OK, 1 row affected (0.12 sec)

以下是使用select命令显示来自该表的记录的查询：

mysql> select *from DemoTable;

这将产生以下输出：

+-------+
| Value |
+-------+
|   -10 |
|   -20 |
|    20 |
|    10 |
|   -10 |
|   -10 |
|   -20 |
|   -30 |
|    30 |
+-------+
9 rows in set (0.00 sec)

以下是按正数和负数值进行分组的查询：

mysql> select *from DemoTable group by -Value;

这将产生以下输出：

+-------+
| Value |
+-------+
|   -10 |
|   -20 |
|    20 |
|    10 |
|   -30 |
|    30 |
+-------+
6 rows in set (0.00 sec)

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