MySQL别名的使用

mysql> create table student(age int(4), name varchar(20));
Query OK, 0 rows affected (0.09 sec)

mysql> insert into student values(21, 'Jack'), (23, 'Rose'), (35, 'Ann'), (56, 'Mike');
Query OK, 4 rows affected (0.06 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from student;
+------+------+
| age  | name |
+------+------+
|   21 | Jack |
|   23 | Rose |
|   35 | Ann  |
|   56 | Mike |
+------+------+
4 rows in set (0.00 sec)

（1）为表取别名

mysql> select * from student s where age > 30;
+------+------+
| age  | name |
+------+------+
|   35 | Ann  |
|   56 | Mike |
+------+------+
2 rows in set (0.00 sec)

mysql>

（2）为字段取别名

mysql> select age as student_age, name as student_name from student;
+-------------+--------------+
| student_age | student_name |
+-------------+--------------+
|          21 | Jack         |
|          23 | Rose         |
|          35 | Ann          |
|          56 | Mike         |
+-------------+--------------+
4 rows in set (0.00 sec)

mysql>