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...
However, this will return NULL provider results as well, how would I exclude all null results?
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.
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).
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
union all. Select 1, 1, 1, NULL ,'Starring : BigStar'.
IS NULL вернёт истину, если операнд имеет значение NULL и ложь, если он им не является.
Word Spark search letters: rep) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,NULL-- qmfQ. Enter first three letters from the first row
I do not want to show revords with null values in any column i only want to only records with data in all column. How can i set that. Please help.
SELECT COALESCE(NULL,'Not NULL','OK'); -- return Not NULL.