select a,b,null,null from table1 union select null,null,c,d from table2 union select null,null,null,null,e,f from table3.
select cast (2000 as type of quint) from rdb$database select cast (2000 as int) from rdb$database.
Note: A NULL value is different from a zero value or a field that contains spaces.
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...
The null character (also null terminator or null byte), abbreviated NUL or NULL, is a control character with the value zero. It is present in many character sets, including ISO/IEC 646 (or ASCII)...
> char array[SIZE] = {0}; Nothing wrong with this. It just assumes that the remaining SIZE-1 elements are also zero, so that's it, job done.
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).
Union select null, null, null, null, null, null -- test all nulls --*/ ). A. DECLARE @ColumnDynamicSQL nvarchar(MAX)
Keeping Null Values Using Default Values with INSERT ...
5.6 If NULL were defined as follows: #define NULL ((char *)0). wouldn't that make function calls which pass an