Ignore NULL values from separate tables in a single MySQL query and display count of NOT NULL records

Let us first create a −

mysql> create table DemoTable1    -> (    -> Id int    -> ); Query OK, 0 rows affected (1.06 sec)

Insert some records in the table using insert −

mysql> insert into DemoTable1 values(1); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1 values(NULL); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1 values(2); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable1 values(3); Query OK, 1 row affected (0.13 sec)

Display all records from the table using select −

mysql> select * from DemoTable1;

This will produce the following output −

+------+ | Id   | +------+ |    1 | | NULL | |    2 | |    3 | +------+ 4 rows in set (0.00 sec)

Following is the query to create second −

mysql> create table DemoTable2    -> (    -> Id int    -> ); Query OK, 0 rows affected (0.65 sec)

Insert some records in the table using insert −

mysql> insert into DemoTable2 values(10); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable2 values(NULL); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable2 values(NULL); Query OK, 1 row affected (0.08 sec)

Display all records from the table using select −

mysql> select * from DemoTable2;

This will produce the following output −

+------+ | Id   | +------+ |   10 | | NULL | | NULL | +------+ 3 rows in set (0.00 sec)

Here is the query to ignore NULL values from separate tables−

mysql> select    -> (    -> select count(Id) from DemoTable1) as CountFirstTableId,    -> (    -> select count(Id) from DemoTable2) as CountSecondTableId    -> ;

This will produce the following output −

+-------------------+--------------------+ | CountFirstTableId | CountSecondTableId | +-------------------+--------------------+ |                 3 |                  1 | +-------------------+--------------------+ 1 row in set (0.00 sec)