原表 :

mysql> desc user;
+-------+----------+------+-----+---------+----------------+
| Field | Type     | Null | Key | Default | Extra          |
+-------+----------+------+-----+---------+----------------+
| id    | int(11)  | NO   | PRI | NULL    | auto_increment |
| name  | char(30) | NO   |     | NULL    |                |
+-------+----------+------+-----+---------+----------------+
2 rows in set (0.01 sec)

查詢結(jié)果1 :

mysql> select * from user;
+----+------+
| id | name |
+----+------+
|  1 | abc  |
|  2 | xyz  |
+----+------+
2 rows in set (0.00 sec)

查詢結(jié)果返回新增is_person字段, 且結(jié)果為"true" :

mysql> select *,"true" as is_person from user;
+----+------+-----------+
| id | name | is_person |
+----+------+-----------+
|  1 | abc  | true      |
|  2 | xyz  | true      |
+----+------+-----------+
2 rows in set (0.00 sec)

as的左邊為新增字段固定值，右邊為新增字段的字段名，如果固定值為數(shù)值型則不用加引號，固定值為其他類型則必須加引號。




原文鏈接