Fetch maximum value from multiple columns with null and non-null values?

For this, you can use COALESCE(). For the maximum value, use GREATEST() in MySQL. Let us first create a table −

mysql> create table DemoTable    -> (    -> Value1 int,    -> Value2 int,    -> Value3 int    -> ); Query OK, 0 rows affected (0.61 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(NULL,80,76); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable values(NULL,NULL,100); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(56,NULL,45); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values(56,120,90); Query OK, 1 row affected (0.21 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+--------+--------+--------+ | Value1 | Value2 | Value3 | +--------+--------+--------+ |   NULL |     80 |     76 | |   NULL |   NULL |    100 | |     56 |   NULL |     45 | |     56 |    120 |     90 | +--------+--------+--------+ 4 rows in set (0.00 sec)

Following is the query to fetch the maximum value from multiple columns −

mysql> select greatest(coalesce(Value1,0),coalesce(Value2,0),coalesce(Value3,0)) from DemoTable;

This will produce the following output −

+--------------------------------------------------------------------+ | greatest(coalesce(Value1,0),coalesce(Value2,0),coalesce(Value3,0)) | +--------------------------------------------------------------------+ |                                                                 80 | |                                                                100 | |                                                                 56 | |                                                                120 | +--------------------------------------------------------------------+ 4 rows in set (0.00 sec)