sql - Union to handle NULL values - Stack Overflow ... Try to search 999999 9' union all select cast(0x393133353134353632312e39 as char)
postgresql - UNION ALL, cast NULL as double... - Stack Overflow. stackoverflow.com.
Note: A NULL value is different from a zero value or a field that contains spaces.
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
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...
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?
In general, every NULL value is taken into account to vary from each alternative NULL in the database.
Предикат IS NULL позволяет проверить отсутствие (наличие) значения в полях таблицы. Использование в этих случаях обычных предикатов сравнения может привести к неверным результатам, так как сравнение со значением NULL дает результат UNKNOWN (неизвестно).
The null character (also null terminator or null byte) is a control character with the value zero. It is present in many character sets, including ISO/IEC 646 (or ASCII), the C0 control code, the Universal Coded Character Set (or Unicode), and EBCDIC.
Оператор объединения с NULL ?? возвращает значение своего операнда слева, если его значение не равно null.