As @Prdp noted, the answer is RDBMS-specific. What is specific is whether the server treats a zero-length string as being equivalent to NULL, which determines whether concatenating a NULL yields a NULL or not.
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...
1 1 1 NULL NULL NULL 2 2 NULL 1 3 1. Then. SELECT COUNT(*), COUNT(Field1), COUNT(Field2), COUNT(DISTINCT Field3) FROM Table1. Output Is: COUNT(*) = 4; -- count all rows, even null/duplicates --.
select (select count(*) from tablea)+(select count(*) from tableb) from dual. Not saying it's better (I can't test it right now so it might not even work!)
(M): SELECT CONCAT(login, password) FROM members. 7. Строки без кавычек Есть несколько
Синтаксис функции COUNT: SELECT COUNT(expression) FROM table WHERE predicates; Функция COUNT принимает один из нескольких параметров
Сюда входят значения NULL и повторяющиеся
Основное использование команды SELECT является просмотр строк из таблицы. Ниже приведен пример команды SELECT, где будет отображать все
The SELECT DISTINCT statement is used to return only distinct (different) values.