Explain Plan is a great way to tune your queries.
As a bonus for using Explain Plan, you will learn more about how the DBMS works “behind the scenes”, enabling you to write efficient queries the first time around.

Explain Plan executes your query and records the “plan” that Oracle devises to execute your query. By examining this plan, you can find out if Oracle is picking the right indexes and joining your tables in the most efficient manner. There are a few different ways to utilize Explain Plan.

The first thing you will need to do is make sure you have a table called plan_table available in your schema.

If this table is not there run this script provided by oracle to create that table
ORACLE_HOME/rdbms/admin/utlxplan.sql .. for UNIX plat formas and
ORACLE_HOME\rdbms\admin\utlxplan.sql .. for WINDOWS platforms

SQL> select * from plan_table;

no rows selected

SQL> explain plan for select * from etr where team=’cis’;
Explained.

SQL>  select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
——————————————————————————–
Plan hash value: 3490786915

—————————————————————————-
| Id  | Operation         | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
—————————————————————————-
|   0 | SELECT STATEMENT  |        |     2 |    30 |     3   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| ETR |     2 |    30 |     3   (0)| 00:00:01 |
—————————————————————————-

Predicate Information (identified by operation id):
—————————————————

PLAN_TABLE_OUTPUT
——————————————————————————–

1 – filter(“TEAM”=’cis’)

13 rows selected.
SQL> @$ORACLE_HOME/rdbms/admin/utlxpls.sql

PLAN_TABLE_OUTPUT
——————————————————————————–
Plan hash value: 3490786915

—————————————————————————-
| Id  | Operation         | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
—————————————————————————-
|   0 | SELECT STATEMENT  |        |     2 |    30 |     3   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS FULL| ETR |     2 |    30 |     3   (0)| 00:00:01 |
—————————————————————————-

Predicate Information (identified by operation id):
—————————————————

PLAN_TABLE_OUTPUT
——————————————————————————–

1 – filter(“TEAM”=’cis’)

13 rows selected.

When you’ve deleted a Table and soon after thyat deletion one of the user created a table with the same name then in that case we have to perform some steps to mitigate the conflict otherwise you’ll recieve error ‘Object trying to create already exists’ and will not allow you to restore the Old Table.

Deleted Table emp1 from system —

SQL> drop table emp1;
Table dropped.

SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME        OBJECT TYPE  DROP TIME
—————- —————————— ———— ——————-
EMP1             BIN$xNis/0KmyEPgQAB/AQBy6Q==$0 TABLE        2012-07-15:12:16:41

Created a table with same name after deletion – emp1 —

SQL> create table emp1 (name varchar2(10));
Table created.
SQL> drop table emp1;
Table dropped.

SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME        OBJECT TYPE  DROP TIME
—————- —————————— ———— ——————-
EMP1             BIN$xNis/0KnyEPgQAB/AQBy6Q==$0 TABLE        2012-07-15:12:17:31
EMP1             BIN$xNis/0KmyEPgQAB/AQBy6Q==$0 TABLE        2012-07-15:12:16:41

Now if i’ll try to Flashback table emp1 then it will restore the one with latest Time Stamp.
SQL>  show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME        OBJECT TYPE  DROP TIME
—————- —————————— ———— ——————-
EMP1             BIN$xNis/0KmyEPgQAB/AQBy6Q==$0 TABLE        2012-07-15:12:16:41
This can also be performed using Time Stamp —
FLASHBACK TABLE emp1 TO TIMESTAMP TO_TIMESTAMP(‘2012-07-15:12:16:41’, ‘YYYY-MM-DD HH:MI:SS’);
During the flashback operation the table can be renamed.
FLASHBACK TABLE flashback_drop_test TO BEFORE DROP RENAME TO flashback_drop_test_old;