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.
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...
(M): SELECT CONCAT(login, password) FROM members. 7. Строки без кавычек Есть несколько
Since a NULL concatenated with a string yields a NULL, we can attempt to build our sub-string and replace a NULL with an empty string, which is then concatenated to the next part of the name. This assumes that FirstName and Surname are always NOT NULL, but you could apply the same logic to...
How can I make GROUPT_CONCAT return NULL if any column is NULL? Here is a test table: CREATE TABLE gc ( a INT(11) NOT NULL, b
Существуют специальные операторы IS NULL и IS NOT NULL, которые позволяют производить сравнения с NULLами.
SELECT id, count(*), count(price>1) FROM usr GROUP BY id. Конечно, в таком виде запрос не сработает.
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, содержимым которого...
Команда IS NULL проверяет поле на NULL. Пример: SELECT * FROM workers WHERE salary IS NULL.
Если инструкция SELECT используется для тестирования на значения NULL в дополнение к другим, она