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...
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.
In general, every NULL value is taken into account to vary from each alternative NULL in the database.
I am getting NULL values in the results of an operation in MySQL. Is there a way to convert the NULL values into the value 0?
Note: A NULL value is different from a zero value or a field that contains spaces.
i am trying to do union i get data with null values and i want do not want it to show in result. such as: column1 col2 col3 col4 col5 col6 test1 1 2 3 null 6 test2 2 3 4 null 6 test3 3 4 5 6 null
Даже выражение NULL != NULL не будет истинным, ведь нельзя однозначно сравнить одну неизвестность с другой.
MySQL allows columns to take "null" (not specified) values by default, so we'd better take a look ...
In MySQL, 0 or NULL means false and anything else means true. The default truth value from a
NULL в Системах управления базами данных (СУБД) — специальное значение (псевдозначение), которое может быть записано в поле таблицы базы данных (БД). NULL соответствует понятию «пустое поле», то есть «поле, не содержащее никакого значения».