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Count only null values in two different columns and display in one MySQL select statement?


1 Answer
Sharon Christine

Use IS NULL to test for NULL value. Let us first create a table −

mysql> create table DemoTable
   -> (
   -> Number1 int,
   -> Number2 int
   -> );
Query OK, 0 rows affected (0.62 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(1,NULL);
Query OK, 1 row affected (0.20 sec)

mysql> insert into DemoTable values(NULL,NULL);
Query OK, 1 row affected (0.15 sec)

mysql> insert into DemoTable values(3,NULL);
Query OK, 1 row affected (0.14 sec)

mysql> insert into DemoTable values(NULL,90);
Query OK, 1 row affected (0.11 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+---------+---------+
| Number1 | Number2 |
+---------+---------+
|      1 | NULL     |
|   NULL | NULL     |
|      3 | NULL     |
|   NULL | 90       |
+---------+---------+
4 rows in set (0.00 sec)

Following is the query to count only null values in two different columns and display in one select statement −

mysql> select
   -> (select count(*) from DemoTable where Number1 is null) as FirstColumnNullValue,
   -> (select count(*) from DemoTable where Number2 is null) as SecondColumnNullValue
   -> ;

This will produce the following output −

+----------------------+-----------------------+
| FirstColumnNullValue | SecondColumnNullValue |
+----------------------+-----------------------+
|                    2 |                     3 |
+----------------------+-----------------------+
1 row in set (0.00 sec)

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