0x31303235343830303536 is NULL - they are just matching the number of columns in your existing query. If you had SELECT * FROM users and users had 4 columns, the UNION must also have 4
Классический вариант внедрения SQL-кода, когда в уязвимый параметр передается выражение, начинающееся с «UNION ALL SELECT».
select a,b,null,null from table1 union select null,null,c,d from table2 union select null,null,null,null,e,f
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)...
Note: A NULL value is different from a zero value or a field that contains spaces.
union all select null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null
when I compare null values the instruccion fails.
create table fruitprices ( id tinyint unsigned not null auto_increment primary key, fruit_id tinyint unsigned not null, price int unsigned not null default 0
R language supports several null-able values and it is relatively important to understand how these values behave, when making data pre-processing and data munging.