-6599 Union All Select Null,null,null,null,null,'qbqvq'||'lxmaauyjqg'||'qqbqq',null,null,null-- Rwer Info

: This is a "fingerprint" or "canary." By concatenating these random strings, the attacker looks for the resulting unique string ( qbqvqLxMaAuyJQgqqbqq ) to appear on the webpage. If it appears, they know which column is vulnerable to displaying data.

: The attacker uses NULL placeholders to match the exact number of columns in the original table. This is a "trial and error" phase used to find the correct database structure without triggering an error. : This is a "fingerprint" or "canary

: This command instructs the database to combine the results of the original (intended) query with a new, malicious query. : This is a "fingerprint" or "canary