A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.
Latest Answer : Transaction is a process by which we take the database from one consistent level to another consistent level. A transaction is said to be completed only when we supply COMMIT and apply the changes to the database. ...
COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user
Latest Answer : all dml operations done previsouly makes permanent in hte database ...
ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.
Latest Answer : ROLLBACK: This is just like UNDO in MSOFFICE but can not REDO, means what ever changes You made after any commit/rollback or A DDL command they will not be saved into database . when rollback is issued your database goes to the stage when ...
For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can
Latest Answer : SavePoint: this is also a TCL command, which puts break points between DML statements so that you can rollback to any point and keeping some part of transaction in process.exampleupdate emp set sal = 500 + sal;savepoint ainser into emp values(.......);savepoint ...
A Read-Only transaction ensures that the results of each query executed in the transaction are consistant with respect to the same point in time.
Latest Answer : it will reads the data firsrt and then executes the transaction ...
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.
Latest Answer : The optimizer determines the most efficient way to use the tables and indexes to complete the request made by an SQL statement after considering many factors related to the objects referenced and the conditions specified in the query. ...
The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.
Latest Answer : The operations that the oracle server performs to execute a SQL statement. ...
What are the different approaches used by Optimizer in choosing an execution plan ?
Rule-based and Cost-based.
The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints
COST and RULE.
Latest Answer : One can specify COST , RULE or CHOOSE for OPTIMIZER _MODE in init.ora file ...
