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.
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 * from(select driverid, name, ssn from drivers where driverid<15 UNION ALL Select driverid,name, cast(null as bigint) from drivers where driverid BETWEEN 18 AND 21) T ; SemanticException 3:48 Schema of both sides of union should match.
E.g. null + null + 1 = 1 null + null + null = null. The problem is that the first expression yields null.
Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
Специальное значение NULL означает отсутствие данных, констатацию того факта, что значение неизвестно. По умолчанию это значение могут принимать столбцы и переменные любых типов, если только на них не наложено ограничение NOT NULL.
R language supports several null-able values and it is relatively important to understand how these
The IS NOT NULL condition is used in SQL to test for a non-NULL value.