Best way to combine multiple advanced MySQL select queries?

To combine multiple advanced MySQL select queries, use UNION. Let us first create a table −

mysql> create table DemoTable1 (Value1 int,Value2 int);
Query OK, 0 rows affected (0.62 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1 values(10,29);
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable1 values(100,190);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable1 values(40,101);
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable1;

This will produce the following output −

+--------+--------+
| Value1 | Value2 |
+--------+--------+
| 10     | 29     |
| 100    | 190    |
| 40     | 101    |
+--------+--------+
3 rows in set (0.00 sec)

Following is the query to create second table −

mysql> create table DemoTable2 (Number1 int, Number2 int);
Query OK, 0 rows affected (0.49 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable2 values(100,290);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable2 values(200,390);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable2 values(50,170);
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable2;

This will produce the following output −

+---------+---------+
| Number1 | Number2 |
+---------+---------+
| 100     | 290     |
| 200     | 390     |
| 50      | 170     |
+---------+---------+
3 rows in set (0.00 sec)

Following is the query to combine multiple advanced MySQL select queries −

mysql> (select Value1,Value2 from DemoTable1)
   union
   (select Number1 AS Value1, Number2 AS Value2 from DemoTable2)
   order by Value1 DESC;

This will produce the following output −

+--------+--------+
| Value1 | Value2 |
+--------+--------+
| 200    |    390 |
| 100    |    290 |
| 100    |    190 |
| 50     |    170 |
| 40     |    101 |
| 10     |     29 |
+--------+--------+
6 rows in set (0.04 sec)