SELECT table name that is inside UNION

I have two same tables. I need to union them in such way:

SELECT f1,f2, xxx
FROM 
(SELECT     *
FROM         tbl1
UNION ALL
SELECT     *
FROM         tbl2)

where xxx would query for a table name开发者_运维问答, where f1 and f2 fields are taken from. Example output:

123 345 'tbl1' -- this rows are from the first table
121 345 'tbl1'
121 345 'tbl1'
123 345 'tbl1'
124 345 'tbl1'
125 345 'tbl2' -- this rows are from the second table
127 345 'tbl2'

Thank you in advance.

---

SELECT f1,f2, xxx
FROM 
(SELECT     *, 'tbl1' as xxx
FROM         tbl1
UNION ALL
SELECT     *, 'tbl2' as xxx
FROM         tbl2)