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.
The Background I was trying to solve the fourth realistic mission in hackthissite.org, and couldn't figure out exactly what SQL I should inject into the URL to retrieve the list of emails.
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...
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as opt however, I
Select null, 'Actual null' from dual union all select '', 'Null string' from dual union all select ' ', 'single
Above is two queries with their results merged by a UNION ALL clause. You will notice that the queries return different columns, one called 'departure' and one called 'arrival'.
What is the difference between … and … and why does the latter not work?
Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left
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.
SQL NULL Values. If a column in a table is optional