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.
Ref: 999999.9' union all select 99,2 and '0'='0.
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 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...
Эта техника работает, когда веб-приложения напрямую возвращают результат вывода команды SELECT на страницу: с использованием цикла for или похожим способом, так что каждая запись полученной из БД выборки последовательно выводится на страницу.
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)...
Number of null-s on change between passed and failed queries is the one attacker looks for.
The IS NOT NULL condition is used in SQL to test for a non-NULL value.
Union select null, null, null, null, null, null -- test all nulls --*/ ). A. DECLARE @ColumnDynamicSQL nvarchar(MAX)