...NULL,NULL,NULL,NULL,NULL,NULL,NULL,CONCAT(0x717a6a7171
UNION ALL SELECT NULL,NULL,NULL,NULL,NULL,CONCAT(0x716b726a71,0x6d4355476f6377717943,0x7163716d71),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...
Since Null is not a member of any data domain, it is not considered a "value", but rather a marker (or placeholder) indicating the absence of value. Because of this, comparisons with Null can never result in either True or False, but always in a third logical result, Unknown.[8] The logical result of the...
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.
Если значение expression равно NULL, IS NULL возвращает TRUE; в противном случае возвращается значение FALSE.If the value of
Suppose that the "UnitsOnOrder" column is optional, and may contain NULL values. Look at the following SELECT statement: SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder) FROM Products; In the example above, if any of the "UnitsOnOrder" values are NULL, the result will be NULL.
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.
Даже выражение NULL != NULL не будет истинным, ведь нельзя однозначно сравнить одну неизвестность с другой.
NULL в Системах управления базами данных (СУБД) — специальное значение (псевдозначение), которое может быть записано в поле таблицы базы данных (БД). NULL соответствует понятию «пустое поле», то есть «поле, не содержащее никакого значения».