select a,b,null,null from table1 union select null,null,c,d from table2 union select null,null,null,null,e,f from table3.
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as
Select null, 'Actual null' from dual union all select '', 'Null string' from dual union all select ' ', 'single
How can I run a MySQL query that selects everything that is not null? It would be something like … Do I just remove the all and go..?
Note: A NULL value is different from a zero value or a field that contains spaces.
Union select null, null, null, null, null, null, null from information_schema.tables. for a small database containing three tables. this instruction is used in sql injection I tried it and it worked but I didn't really know how it works can somebody help me...
What is the difference between … and … and why does the latter not work?
Thus even though you have casted null to match ssn's datatype bigint, you must give it an alias as shown below. Select*from(select driverid, name, ssn from drivers where driverid<15. UNION ALL. Select driverid,name, cast(nullas bigint) as ssn from drivers where driverid BETWEEN 18 AND 21) T.
Is there a way to set a char variable to 0 or null or something so that it will basically reset my control variable.
The IS NOT NULL condition is used in SQL to test for a non-NULL value. It returns TRUE if a non-NULL value is found, otherwise it returns FALSE. It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.