{keyword}) Union All Select Null,null,null,null,null-- Zkhd May 2026

The string you provided is a designed to discover the number of columns in a database table. Breakdown of the Payload

: This command combines the result set of the original query with a new set of data. UNION ALL is used instead of UNION because it is often faster and does not remove duplicates, which can be useful for certain types of data extraction. {KEYWORD}) UNION ALL SELECT NULL,NULL,NULL,NULL,NULL-- ZkhD

: This is likely a random string or a "signature" used by a vulnerability scanner (like Burp Suite or sqlmap) to track if the payload was successfully reflected in the application's response. The string you provided is a designed to

: This is a comment indicator that tells the database to ignore the rest of the original query that follows. : This is likely a random string or

An attacker (or security researcher) would send this payload to an application to see if it returns an error or a successful response.

: The attacker uses a specific number of NULL values to match the number of columns in the original query's SELECT statement. NULL is used because it is compatible with almost any data type (strings, integers, dates), maximizing the chance that the injected query will succeed.

: The number of NULL values (5 in this case) does not match the number of columns in the original table.