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...
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.
However, this will return NULL provider results as well, how would I exclude all null results?
The IS NOT NULL operator is used to test for non-empty values (NOT NULL values). The following SQL lists all customers with a value in the "Address" field: Example. SELECT CustomerName, ContactName, Address FROM Customers WHERE Address IS NOT NULL
union all. Select 1, 1, 1, NULL ,'Starring : BigStar'.
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 IS NOT NULL condition is used in SQL to test for a non-NULL value. It returns TRUE if a non-NULL value is found, otherwise it returns FALSE.
Word Spark search letters: rep) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,NULL-- uktO. Enter first three letters from the first row
select NULL customer, 'MOLOKO' product, 2 qty from dual union all --. Иван купил 2 молока.
NULL is special in SQL. NULL indicates that the data is unknown, inapplicable or even does not