{keyword}' Union All Select Null-- Fhda »

The initial ' (single quote) is used to "break out" of a predefined data field in a website's code. If the application isn't properly sanitizing inputs, this quote tells the database that the original command has ended and a new one is beginning. 2. The UNION ALL Operator

The -- (double dash) is the SQL syntax for a comment. Everything following these dashes is ignored by the database. This is used to "comment out" the rest of the original, legitimate code (like a closing quote or a WHERE clause) that would otherwise cause a syntax error and crash the attack. {KEYWORD}' UNION ALL SELECT NULL-- FHDA

While "FHDA" likely refers to a specific target or internal tracking tag used by a security researcher or a tool, the string itself is a classic example of an . To prevent such attacks, developers should always use parameterized queries (prepared statements) rather than building queries with raw user input. The initial ' (single quote) is used to