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
If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, ... which covers (int *)0 as null pointer since cast is an
then using zero makes more sense (as in if you use NULL, you cannot logically use p && !q - you need to explicitly compare against NULL, unless you assume NULL is zero, in which case why use NULL). Is there any objective reason to prefer zero over NULL (or vice versa), or is all just personal preference?
Then in the second table I have select ..., null as opt from... I know that I could have an empty string with '' as.
1' UNION SELECT @--+ #The used SELECT statements have a different number of columns 1' UNION SELECT @,@--+ #The used
SQL NULL Functions. ❮ Previous Next ❯.
If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.”
Подскажите, пожалуйста, что значит "NULL", и когда он применяется ? В примере ниже , насколько я понимаю, создаётся строка
NULL в языках программирования Си и C++ — макрос, объявленный в заголовочном файле stddef.h (и других заголовочных файлах). Значением этого макроса является зависящая от реализации константа нулевого указателя (англ. null pointer constant).