Count SQL

SELECT columns FROM table_a
UNION
SELECT columns FROM table_b

The UNION statement combines two different SQL queries into a single result set. UNION is most commonly used with the SELECT statement and joins & left joins to combine the required data from several different tables.

Note: UNION will remove duplicate rows from the result.

Imagine we have 2 tables table_a and table_b.

   table_a                  table_b
------------------      ----------------
|item    |name   |      |item   |name  |
------------------      ----------------
|1       |widget |      |4      |pen   |
------------------      ----------------
|2       |frob   |      |5      |pencil|
------------------      ----------------
|3       |gizmo  |
------------------

Now we will perform the union.

SELECT * FROM table_a
UNION
SELECT * FROM table_b;
------------------ 
|item    |name   | 
------------------  
|1       |widget |  
------------------   
|2       |frob   | 
------------------ 
|3       |gizmo  |
------------------
|4       |pen    |
------------------
|5       |pencil |
------------------