I try to select from one table like this:
SELECT * FROM table1 where id=311
and date BETWEEN '2012-09-01' And '2012-09-09'
and col2='a'
and (col3 ='m'
or col3 ='n'
or col3=' ' )
ORDER BY date
In the table I have situation where col3 has values ‘m’, ‘n’ or null, but this select doesn’t return rows where col3 has a null value
NULLis something other than' 'usecol3 is null