mysql - sql怎么标识查出的记录是来自哪个表

Question

select * form a
union all
select * form b
limit 0，10
查出来后，我想再人为加一个字段，标识这条记录是a还是b表的，应该怎么做

Answer 1

SELECT  a.* ,
        "A" AS `from_table`
FROM    a
UNION ALL
SELECT  b.* ,
        "B" AS `from_table`
FROM    b
LIMIT   0, 10

http://sqlfiddle.com/#!2/4d3379/2