QUERY PROCESSOR: The query processor is used to interpret the online user’s query and convert it into an efficient series of operations in a form capable of being sent to the storage manager for execution. The query processor uses the data dictionary to find the structure of the relevant portion of the database and uses this information in modifying the query and preparing an optimal plan to access the database. The query processor component include
DML Compiler: Which translates DML statements in a query language into low-level instructions that the query evaluation engine understands? In addition it transforms the query into an equivalent but more efficient form.
Embedded DML Precompiler : which converts DML statements embedded in an application program to normal procedure calls in the host language.
Data Definition Language Interpreter: The DDL compiler converts the data definition statements into a set of tables. These tables contain the metadata concerning the database and are in a form that can be used by other components of the DBMS.
Query Evaluation Engine: This executes low-level instructions generated by the DML compiler.
