Mysql query WHERE clause not working. WHERE useDate<>CURDATE()

Question

useDate is date type and is NULL . The query below doesn't work

UPDATE licenses 
     SET useDate = CURDATE() 
WHERE license = 'ABC123' AND useDate <> CURDATE();

Answer 1

Your problem is the where clause -- NULL values don't match <> or = . You can do:

UPDATE licenses 
     SET useDate = CURDATE() 
WHERE license = 'ABC123' AND
      (useDate <> CURDATE() or useDate IS NULL);

Or use MySQL's NULL-safe comparison:

UPDATE licenses 
     SET useDate = CURDATE() 
WHERE license = 'ABC123' AND
      NOT (useDate <=> CURDATE());

Answer 2

SQL 101: NULL is not equal to anything. Likewise, NULL is not not-equal to anything. Use IS NULL in such situations:

UPDATE licenses
SET useDate = CURDATE()
WHERE license = 'ABC123' AND (useDate IS NULL OR useDate <> CURDATE());

Answer 3

convert date and use Trim on license column in case of any blank space

UPDATE licenses 
         SET useDate = date(now())
    WHERE Trim(license) = 'ABC123' AND date(useDate)!= date(now());

Answer 4

could be you have a datetime for useDate

    UPDATE licenses 
         SET useDate = CURDATE() 
    WHERE license = 'ABC123' AND date(useDate) != CURDATE();

so you need to compare the date part

Answer 5

That request worked for me ;)

UPDATE licenses 
SET useDate = CURDATE() 
WHERE license = 'ABC123' AND (useDate IS NULL OR useDate <> CURDATE());