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...
11223344) UNION SELECT NULL,NULL,NULL,NULL WHERE 1=2 –- Если нет ошибки, значит синтаксис верный, т.е. используется MS SQL Server.
Coming to our discussion, NULL macro is defined as ((void *)0) in header files of most of the C compiler implementations. But C standard is saying that 0 is also a null pointer constant.
Как и в случае с обычными переменными, указатели не инициализируются при создании. Если значение не было присвоено, то указатель по умолчанию будет указывать на любой адрес...
Union select null, null, null, null, null, null, null from information_schema.tables
The null character (also null terminator or null byte), abbreviated NUL or NULL, is a control character with the value zero. It is present in many character
UNION ALL SELECT NULL, *, NULL, NULL FROM email. I understand what this does and why; the hacker needs to create a query that has the same number of columns as the query it's being merged with, and shifted around the * to make sure the emails are displayed. That's not my question.
http://www.itamed.com/mcms/itamedt/content.cfm?pulldata=scmsmembers.cfm&function=members&perform=memberappita&entity_id=11+limit+0+UNION+SELECT+1,2,concat_ws(0x3a,user(),version
Существуют специальные операторы IS NULL и IS NOT NULL, которые позволяют производить сравнения с NULLами. IS NULL вернёт истину, если операнд имеет значение NULL и ложь, если он им не является.
The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field: Example. SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NULL