Query Processor: As query is very much necessary to find out only the data user need from tons of data of the database, query processor is very important to process these query requests. Query processors come with the following components,
- DDL Interpreter: It interprets the DDL statements and records the definitions in data dictionary.
- DML Compiler: It translates the DML statements in a query language into an evaluation plan consisting of low-level instructions that the query evaluation understands. It also performs query optimization which actually picks up the lowest cost evaluation plan from various alternatives.
- Query Evaluation Engine: It executes the low level instruction compiled by the DML compiler.