让我们说我有两个桌子A，B


    A: NAME, ID, BIRTHDAY, COUNTRY
---------------------------------------
       john, ab123, 12/21/1999, USA
       JANE, as111, 11/02/1956, FRANCE

    B: NAME, ID, SALARY
---------------------------------------
       MARY, AS111, 12333


I WANT TO JOIN TWO TABLES WITH THESE COLUMNS :
NAME, ID, FROM_WHERE
-------------------------------
john, ab123, 'A'
JANE, as111, 'A'
MARY, AS111, 'B'

如果该值源自B.

SELECT NAME, ID FROM A JOIN B USING (NAME, ID)

通过上面的查询，我应该添加什么来获取FROM_WHERE值？

分析解答

您可以使用UNION这样做：

SELECT NAME, ID, 'A' as FROM_TABLE from A 
UNION ALL
SELECT NAME, ID, 'B' as FROM_TABLE from B 
ORDER by NAME;