Basic Oracle Concepts and Programming Question:

Answer #1If your user account has autotrace configured by the DBA, you can use the "SET AUTOTRACE ON EXPLAIN" command to turn on execution path reports on query statements. The tutorial exercise bellow shows you a good example:

SQL> CONNECT HR/retneclgg

SQL> SET AUTOTRACE ON EXPLAIN

SQL> SELECT E.LAST_NAME, E.SALARY, J.JOB_TITLE
2 FROM EMPLOYEES E, JOBS J
3 WHERE E.JOB_ID=J.JOB_ID AND E.SALARY>12000;
<pre>LAST_NAME SALARY JOB_TITLE
----------------- ---------- -----------------------------
King 24000 President
Kochhar 17000 Administration Vice President
De Haan 17000 Administration Vice President
Russell 14000 Sales Manager
Partners 13500 Sales Manager
Hartstein 13000 Marketing Manager</pre>
6 rows selected.

Answer #2Execution Plan
-----------------------------------------------------------
Plan hash value: 3851899397
<pre>
-----------------------------------------------------------
Id|Operation |Name |Rows|Bytes| Cost|Time
| | | | |/%CPU|
-----------------------------------------------------------
0|SELECT STATEMENT | | 59| 2832| 4/0|00:00:01
1| NESTED LOOPS | | 59| 2832| 4/0|00:00:01
*2| TABLE ACCESS FULL |EMPLOYEES| 59| 1239| 3/0|00:00:01
3| TABLE ACCESS |JOBS | 1| 27| 1/0|00:00:01
| BY INDEX ROWID | | | | |
*4| INDEX UNIQUE SCAN|JOB_ID_PK| 1| | 0/0|00:00:01
-----------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("E"."SALARY">12000)
4 - access("E"."JOB_ID"="J"."JOB_ID")
</pre>