This project is aimed at hacking into internals of a simple Database System -- SimpleDB. SimpleDB only implements a small portion of SQL using simple algorithms. This project extends its functions and improves its efficiency.

This project extends SimpleDB SQL, like adding JOIN, AS, adding aggregate operators COUNT, SUM, AVG with a GROUP BY clause, and ORDER BY clause with DESC option.

This project achieved implementing BTree index and selectivity to achieve query optimization, speeding up query procedure.