: This is an intentional "invalid" input (like a negative ID) designed to break the original SQL query's logic and ensure the database returns no results for the first part of the operation.
The string -3216' UNION ALL SELECT 34,34,34,34# is a classic example of a used to exploit vulnerabilities in database-driven applications. Breaking Down the Payload -3216' UNION ALL SELECT 34,34,34,34#
: This part creates a "fake" row of data. Attackers use this to determine the exact number of columns required for the UNION to work, as both queries must have the same number of columns. : This is an intentional "invalid" input (like