mysql - 根据我从中选择的表设置 View 的列值

Question

我正在从 2 个表创建一个 View 。我需要在 View 中创建一个全新的列；当我从第一个表中选择时，此列必须设置为 0，从第二个表中选择时必须设置为 1:

Table A:
+---------+---------+
|column A |column B |
+---------+---------+
|  Boston |   USA   |
+---------+---------+
| Chicago |   USA   |
+---------+---------+
|Las Vegas|   USA   |
+---------+---------+

Table B:
+---------+---------+
|column A |column B |
+---------+---------+
|  Paris  |  Europe |
+---------+---------+
|  Madrid |  Europe |
+---------+---------+
|  London |  Europe |
+---------+---------+

Resulting View:
+---------+---------+---------+
|column A |column B | column C|
+---------+---------+---------+
|  Boston |   USA   |    0    |
+---------+---------+---------+
| Chicago |   USA   |    0    |
+---------+---------+---------+
|Las Vegas|   USA   |    0    |
+---------+---------+---------+
|  Paris  |  Europe |    1    |
+---------+---------+---------+
|  Madrid |  Europe |    1    |
+---------+---------+---------+
|  London |  Europe |    1    |
+---------+---------+---------+

Answer 1

只需使用带有计算列的并集:

SELECT columnA, columnB, 0 AS columnC FROM TableA
UNION ALL
SELECT columnA, columnB, 1 FROM TableB
ORDER BY columnC;