MySQL query to count all the column values from two columns and exclude NULL values in the total count?

Let us first create a table −

mysql> create table DemoTable1975
   (
   StudentName varchar(20),
   StudentMarks int
   );
Query OK, 0 rows affected (0.00 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable1975 values('John',45);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1975 values('Chris',67);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1975 values('David',59);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1975 values('Bob',NULL);
Query OK, 1 row affected (0.00 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable1975;

This will produce the following output −

+-------------+--------------+
| StudentName | StudentMarks |
+-------------+--------------+
| John        |           45 |
| Chris       |           67 |
| David       |           59 |
| Bob         |         NULL |
+-------------+--------------+
4 rows in set (0.00 sec)

Here is the query to count all the column values −

mysql> select count(StudentName)+count(StudentMarks) from DemoTable1975;

This will produce the following output −

+----------------------------------------+
| count(StudentName)+count(StudentMarks) |
+----------------------------------------+
|                                      7 |
+----------------------------------------+
1 row in set (0.00 sec)