sql - CONCAT'ing NULL fields - Stack Overflow | Post as a guest. stackoverflow.com.
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...
UNION ALL SELECT NULL, *, NULL, NULL FROM email. I understand what this does and why; the hacker needs to create a query that has the same number of columns as the query it's being merged with, and shifted around the * to make sure the emails are displayed. That's not my question.
Перевод отдельных слов, фраз, а также целых текстов и веб-страниц (английский, немецкий, французский, испанский, польский и др.).
11223344) UNION SELECT NULL,NULL,NULL,NULL WHERE 1=2 –- Если нет ошибки, значит синтаксис верный, т.е. используется MS SQL Server.
...Null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,concat
Существуют специальные операторы IS NULL и IS NOT NULL, которые позволяют производить сравнения с NULLами.
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 field.
Null values and null pointers. Just like normal variables, pointers are not initialized when they are instantiated. Unless a value is assigned, a pointer
Appends encoded NULL byte character at the end of payload.