SQL-инъекции: UNION атаки | Заметки разработчика
Причина использования NULL в качестве значений возвращаемых из внедрённого запроса SELECT, заключается в том, что типы данных в каждом столбце должны быть совместимы между исходным и внедрённым запросами.
SQL UNION Operator
The UNION operator is used to combine the result-set of two or more SELECT statements. Every SELECT statement within UNION must have the same number of columns.
sql injection "union select null" - CodeProject
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...
Mysql – How null is treated using union and union all in thesql...
As null <> null then how the value null is treated here and in which datatype it is considered.
SQL: UNION ALL Operator
The SQL UNION ALL operator is used to combine the result sets of 2 or more SELECT statements. It does not remove duplicate rows between the various SELECT statements (all rows are returned).
You see the following in the logs: ' UNION ALL SELECT null... - Skillset
Explanation. The UNION keyword combines more than one query, the second query is used by the attacker to find out information about the structure of the database.
Lab: SQL injection UNION attack, finding a column containing text
Try replacing each null with the random value provided by the lab, for example: '+UNION+SELECT+'abcdef',NULL,NULL--. If an error occurs, move on to the next null and try that instead.
Объединение UNION и UNION ALL в SQL – описание и примеры
В этой заметки мы рассмотрим объединение UNION и UNION ALL в языке SQL и напишем несколько примеров в Microsoft SQL Server.
PostgreSQL IS NULL
In the database world, NULL means missing information or not applicable. NULL is not a value, therefore, you cannot compare it with any other values like numbers or strings. The comparison of NULL with a value will always result in NULL, which means an unknown result.
SQL UNION overview, usage and examples
This article provides overview of the SQL UNION operator, along with examples and explore some common questions like the differences between UNION vs UNION ALL.