To design the database and tune SQL Queries. Tuning can be done by reducing the total CPU time and reducing the input taken by the Query. This tool can be used by the developer to tune the queries and to examine Nested and normalized queries, and information about database objects. The input to the optimizer is a parsed SQL query and statistics about the tables, indexes, and columns named in the query. The optimizer examines parsed and normalized queries, and information about database objects. The input to the optimizer is a parsed SQL query and statistics about the tables, indexes, and columns named in the query. The output from the optimizer is a query plan. The query plan is compiled code that contains the ordered steps to carry out the query, including the access methods (table scan or index scan, type of join to use, join order, and so on) to access each table. Using statistics on tables and indexes, the optimizer predicts the cost of using alternative access methods to resolve a particular query. It finds the best query plan – the plan that is least costly in terms of input.