Question

I have 2 tables. 1 table have 3 rows and another table have 5 rows. I wanted to join this both tables together and the result should show 3rows and 5 rows respectively. Is there any ways that could achieve that using sql statement? Any help will be appreciated.

Answer 1

You can use UNION for this,

SELECT colA, colB, colC, 1 as OrderThis
FROM tableA
UNION ALL
SELECT colA, colB, colC, 2 as OrderThis
FROM tableB
ORDER BY OrderThis ASC

There are two basic rules of using UNION

• the number of columns must be the same from both queries
• the data types must be compatible

UNION has an optional parameter ALL. if you omit ALL parameter, UNION will distinctly display all unique records that were combined.

As you can see, I have added a virtual column OrderThis. This will be the basis for the ordering of your rows. But the Problem is it will show on your result list. the solution is by wrapping it in a subquery,

SELECT colA, colB, colC
FROM
(
    SELECT colA, colB, colC, 1 as OrderThis
    FROM tableA
    UNION ALL
    SELECT colA, colB, colC, 2 as OrderThis
    FROM tableB
) a
ORDER BY OrderThis ASC