The string you provided is a designed to test for or exploit vulnerabilities in a database's search or filtering "feature."
In short, this is not a legitimate feature of a software product, but rather a used to see if a website is properly "sanitizing" the text that users type into search bars or forms. The string you provided is a designed to
: This is likely a unique "fingerprint" or tag used by security researchers or automated scanning tools to identify if the injected code was successfully executed in the results. The attacker adds NULL values until the query
: This is used to determine the number of columns being returned by the original query. The attacker adds NULL values until the query stops returning an error, revealing the database structure. The string you provided is a designed to
: This is a SQL comment. It tells the database to ignore everything that follows it, which prevents any remaining original code from causing a syntax error.