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
11223344) UNION SELECT NULL,NULL,NULL,NULL WHERE 1=2 –- Если нет ошибки, значит синтаксис верный, т.е. используется MS SQL
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
...NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,CONCAT%28version(),0x3a,user
Соответственно, IS NOT NULL действует наоборот: вернёт истину, если значение операнда отлично от NULLа и ложь, если он является NULLом
In this table I need to select only the ids which have both null and not null marks, and it should not be both not null or both are null in col1.
By specifically mentioning NULL pointer, C standard gives mechanism using which a C programmer can use and check whether a given pointer is legitimate or not. But what exactly is NULL and how it’s defined? Strictly speaking, NULL expands to an implementation-defined null pointer constant which is...
Тогда это NULL-значение будет заменено на следующее сразу же за ним определённое значение.
UNION SELECT GROUP_CONCAT(column_name) FROM information_schema.columns WHERE table_name
Разрешение значений NULL в определениях столбцов вводит в приложение логику трех значений.Allowing null values in column