CHR(100)||CHR(85)||CHR(102)||CHR(83) translates to the string "dUfS" .The code asks the database: "Does dUfS equal dUfS?" Since this is always true, the database will process the request without an error.
This specific payload is likely a test.
If the website loads normally, the attacker knows the database processed the "True" statement ( dUfS = dUfS ) successfully. The payload uses AND statements
The payload uses AND statements. For the database to return a result, the conditions following the AND must be true. You can stop these attacks by using (Prepared Statements)
If you are a developer, seeing this in your logs means someone is scanning your site for holes. You can stop these attacks by using (Prepared Statements). This ensures the database treats input as "just text" rather than executable code, rendering the single quotes and CHR commands harmless. The payload uses AND statements