如何在MySQL计算中使用别名？

让我们首先创建表格。创建表格的查询语句如下所示 –

mysql> create table AliasDemo
   −> (
   −> Id int
   −> );
Query OK，0 rows affected (0.52 sec)

使用insert命令将一些记录插入表格。以下是插入记录的查询语句 –

mysql> insert into AliasDemo values(20);
Query OK，1 row affected (0.45 sec)

mysql> insert into AliasDemo values(30);
Query OK，1 row affected (0.20 sec)

mysql> insert into AliasDemo values(40);
Query OK，1 row affected (0.83 sec)

现在可以使用select语句显示所有记录 –

mysql> select *from AliasDemo;

以下是输出结果 –

+------+
| Id   |
+------+
|   20 |
|   30 |
|   40 |
+------+
3 rows in set (0.00 sec)

下面是在计算中设置别名的查询语句 –

mysql> select Id,100 as MyNumber ,(select MyNumber)*Id as MultiplyWith100 from AliasDemo;

以下是输出结果 –

+------+----------+-----------------+
| Id   | MyNumber | MultiplyWith100 |
+------+----------+-----------------+
|   20 |      100 |            2000 |
|   30 |      100 |            3000 |
|   40 |      100 |            4000 |
+------+----------+-----------------+
3 rows in set (0.00 sec)

可以在单一执行中实现它。以下是查询语句 –

mysql> select 100 as MyNumber,(select MyNumber)*10 as MultiplyWith100;

以下是输出结果 –

+----------+-----------------+
| MyNumber | MultiplyWith100 |
+----------+-----------------+
|      100 |            1000 |
+----------+-----------------+
1 row in set (0.00 sec)

阅读更多：MySQL 教程