Question

+------+
| num  |
+------+
|    1 |
|    2 |
|    3 |
| NULL |
|    5 |
|    6 |
+------+

This is table test.

select max(num) from test;   ---> 6

How to write a SQL statement that
if NULL values exists –> output should be “OK”

if NULL values does not exist in this column –> output should be 6

I try many times but no luck. Any help?
It would be nice if the solution is ANSI SQL

Answer 1

Try this: http://www.sqlfiddle.com/#!2/dfcbd/2

This:

CREATE TABLE tbl
    (`num` int);

INSERT INTO tbl
    (`num`)
VALUES
    (1),
    (2),
    (3),
    (NULL),
    (5),
    (6);

select if(bit_or(num is null), 'OK', max(num)) as max from tbl;

Outputs:

OK

This:

CREATE TABLE tblx
    (`num` int);

INSERT INTO tblx
    (`num`)
VALUES
    (1),
    (2),
    (3),    
    (5),
    (6);

select if(bit_or(num is null), 'OK', max(num)) as max from tblx;

Outputs:

6