Mix records of two different tables - sql

Question

I'm looking for a way to solve my SQL problem.
I have 2 tables in Firebird 2.5 ( T1 and T2 ) like these:
T1 (
T1_ID INTEGER,
T1_DAY DATE,
T1_NAME VARCHAR(200)
)
T2 (
T2_ID INTEGER,
T2_DAY DATE,
T2_NAME VARCHAR(200)
)
I need a query that mixes records of those tables and sort them in ascending date order. I don't care if a join query increases the number of fields or the date field is not the same as result or stored procedures are needed.
Example output
T1_ID T1_DAY T1_NAME T2_ID T2_DAY T2_NAME
---------------------------------------------------
1 01/02/2011 BOB NULL NULL NULL
2 27/02/2011 SAM NULL NULL NULL
NULL NULL NULL 8 15/03/2011 PETER
NULL NULL NULL 10 21/03/2011 JOHN
6 17/04/2011 AMY NULL NULL NULL
or (better output)
ID DAY NAME
-------------------------
1 01/02/2011 BOB
2 27/02/2011 SAM
8 15/03/2011 PETER
10 21/03/2011 JOHN
6 17/04/2011 AMY

Answer 1

You want the UNION operator:
SELECT
T1.T1_ID ID,
T1.T1_DAY DAY,
T1.T1_NAME NAME
FROM
T1
UNION
SELECT
T2.T2_ID,
T2.T2_DAY
T2.T2_NAME
FROM
T2
;
You can make the individual selects have any additional features you like. The only restriction is that all of the columns in both of the select lists are in the same order and have the same type (they are "union compatible"). The resulting rows will have column headings like the first select.
edit: To control the ordering of a union, you'll have to do the union in a subselect and the ordering in the outer query.
SELECT u.ID, u.DAY, u.NAME
FROM (
SELECT T1.T1_ID ID, T1.T1_DAY DAY, T1.T1_NAME NAME
FROM T1
UNION
SELECT T2.T2_ID, T2.T2_DAY T2.T2_NAME
FROM T2
) u
ORDER BY u.NAME;