The order of clauses in a SQL statement should have no relation on the order of execution because SQL is a declarative query language. The query specifies what

The order of clauses in a SQL statement should have no relation on the order of execution because SQL is a declarative query language. The query specifies what the user wants and not how the system should compute the answer. This declarative property also provides a (somewhat weak) motivation of why SELECT should come first. Precisely because it answers part of the WHAT, i.e., the schema of the result.