No dependency sub-clauses are sub-clauses that do not reference a table. These types of sub-clause are of little use in a query, but may exist as they are valid SQL.
During the ‘Determine Sub-Clause Type’ phase of the optimization algorithm, the Query Processor identifies any no-dependency sub-clauses in your query and uses them to create a special condition.
At the very start of the query’s execution phase (see SQL Execution), the Query Processor evaluates the no-dependency sub-clause ‘special condition’. If it is true, the query is executed, the search is performed and the appropriate result set is returned; if it is false, the query is not executed, the search is not performed and an empty result set is returned.
The execution phase of a query comes after the Parse, Verify, and Optimize phases.