Keep values separate from instructions
A database query has structure and values. Parameter binding lets a database driver pass a value separately from the SQL that describes the operation.
Protect the boundary on the server
Browser validation helps people enter useful data, but a caller can send a request without using your form. Authorization and database query safety belong at trusted server boundaries.
Defense in depth
Use parameter binding, validate business rules, apply authorization, and keep secrets outside public code. Each control has its own purpose.