Can users see the query plan of a SQL query in Oracle?

Question

Hi,
I wonder for a given sql query, after the system optimization, can I see the query plan in oracle? If yes, how to do that? thank you.
Xing

Answer 1

You can use explain plan in SQLPlus
SQL>  explain plan for select * from user_tables;
Explained.
Elapsed: 00:00:01.63
SQL> select * from table(dbms_xplan.display());
PLAN_TABLE_OUTPUT
Plan hash value: 806004009
| Id  | Operation                       | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT                |          |  2014 |  1123K|   507   (6)| 00:00:07 |
|*  1 |  HASH JOIN RIGHT OUTER          |          |  2014 |  1123K|   507   (6)| 00:00:07 |
|   2 |   TABLE ACCESS FULL             | SEG$     |  4809 |   206K|    34   (3)| 00:00:01 |
|*  3 |   HASH JOIN RIGHT OUTER         |          |  1697 |   873K|   472   (6)| 00:00:06 |
|   4 |    TABLE ACCESS FULL            | USER$    |    74 |  1036 |     3   (0)| 00:00:01 |
|*  5 |    HASH JOIN OUTER              |          |  1697 |   850K|   468   (6)| 00:00:06 |
|   6 |     NESTED LOOPS OUTER          |          |  1697 |   836K|   315   (6)| 00:00:04 |
|*  7 |      HASH JOIN                  |          |  1697 |   787K|   226   (8)| 00:00:03 |
|   8 |       TABLE ACCESS FULL         | TS$      |    13 |   221 |     5   (0)| 00:00:01 |
|   9 |       NESTED LOOPS              |          |  1697 |   759K|   221   (8)| 00:00:03 |
|  10 |        MERGE JOIN CARTESIAN     |          |  1697 |   599K|   162  (10)| 00:00:02 |
|* 11 |         HASH JOIN               |          |     1 |   326 |     1 (100)| 00:00:01 |
|* 12 |          FIXED TABLE FULL       | X$KSPPI  |     1 |    55 |     0   (0)| 00:00:01 |
|  13 |          FIXED TABLE FULL       | X$KSPPCV |   100 | 27100 |     0   (0)| 00:00:01 |
|  14 |         BUFFER SORT             |          |  1697 | 61092 |   162  (10)| 00:00:02 |
|* 15 |          TABLE ACCESS FULL      | OBJ$     |  1697 | 61092 |   161  (10)| 00:00:02 |
|* 16 |        TABLE ACCESS CLUSTER     | TAB$     |     1 |    96 |     1   (0)| 00:00:01 |
|* 17 |         INDEX UNIQUE SCAN       | I_OBJ#   |     1 |       |     0   (0)| 00:00:01 |
|  18 |      TABLE ACCESS BY INDEX ROWID| OBJ$     |     1 |    30 |     1   (0)| 00:00:01 |
|* 19 |       INDEX UNIQUE SCAN         | I_OBJ1   |     1 |       |     0   (0)| 00:00:01 |
|  20 |     TABLE ACCESS FULL           | OBJ$     | 52728 |   411K|   151   (4)| 00:00:02 |
Predicate Information (identified by operation id):
   1 - access("T"."FILE#"="S"."FILE#"(+) AND "T"."BLOCK#"="S"."BLOCK#"(+) AND
              "T"."TS#"="S"."TS#"(+))
   3 - access("CX"."OWNER#"="CU"."USER#"(+))
   5 - access("T"."DATAOBJ#"="CX"."OBJ#"(+))
   7 - access("T"."TS#"="TS"."TS#")
  11 - access("KSPPI"."INDX"="KSPPCV"."INDX")
  12 - filter("KSPPI"."KSPPINM"='_dml_monitoring_enabled')
  15 - filter("O"."OWNER#"=USERENV('SCHEMAID') AND BITAND("O"."FLAGS",128)=0)
  16 - filter(BITAND("T"."PROPERTY",1)=0)
  17 - access("O"."OBJ#"="T"."OBJ#")
  19 - access("T"."BOBJ#"="CO"."OBJ#"(+))
42 rows selected.
Elapsed: 00:00:03.61
SQL> If your plan table does not exist, execute the script $ORACLE_HOME/RDBMS/ADMIN/utlxplan.sql to create the table.