The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.
Considering available access paths and determining the most efficient execution plan based on statistics in the data dictionary for the tables accessed by the statement and their associated clusters and indexes.
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.
Commit, Rollback, DCL command like grant revoke.When exit from oracle (implicite commit happened), When database abnormally closed then an implicit rollback happened. When user invokes an DDl command
select to_number(rollnumber) from tname order by rollnumber
Rule-based and Cost-based.
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.