Oracle Property Manager Tables:

Oracle Property Manager Views:

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First you learn that is the big question, are you searching the term index what is it

What is index?

Indexes are optional structures that associated with tables and clusters.

Why use index?

Index allow SQL queries to execute more quickly against a table.

Index in manual helps that you can locate information faster data retrieve, if there were no index.

Oracle Database index provides a faster access path to table data.

Note

1. Index apply and Create and recreate After Inserting Table Data, or already data exists in the table.
2. Multiple indexes on the same column list a very bad idea.
3. LONG and LONG RAW columns cannot be indexed.
4. The Primary and unique keys automatically have indexes, but you might want to create an index on a foreign key.

Indexes in Oracle Database 12c

From an indexing perspective in oracle database 12c , one of the bigger ticket items introduced with in the new capability to create multiple indexes on the same column list.

The Oracle database 12c allows the multiple indexes on the same set of columns, provided only one index is visible and all indexes are different in some way.

Non-Partitioned Tables

The non-partitioned indexes, the optimizer does not consider any unusable indexes when creating an access plan for SELECT statements. The only exception is when an index is explicitly specified with the INDEX() hint.

Create the following table.

DROP TABLE test1 PURGE;

CREATE TABLE test1 (
  id            NUMBER,
  description   VARCHAR2(50),
  created_date  DATE
);

INSERT INTO test1 VALUES (1, 'test1 ONE', TO_DATE('01/07/2011', 'DD/MM/YYYY'));
INSERT INTO test1 VALUES (2, 'test1 TWO', TO_DATE('01/07/2012', 'DD/MM/YYYY'));
INSERT INTO test1 VALUES (3, 'test1 THREE', TO_DATE('01/07/2013', 'DD/MM/YYYY'));
COMMIT;

When we create the first index, it works as expected.

SQL> CREATE INDEX test1_idx1 ON test1(created_date) VISIBLE;

Index created.

If we attempt to create an invisible index on the same set of columns it fails because it has the same attributes are the existing index.

SQL> CREATE INDEX test1_idx2 ON test1(created_date) INVISIBLE;
                           *
ERROR at line 1:
ORA-01408: such column list already indexed

SQL>

If we alter something about it, like make it a bitmapped index, it works.

CREATE BITMAP INDEX test1_idx3 ON test1(created_date) INVISIBLE;

Index created.

SQL>

Partitioned Tables

Partitioned index where one or more of the partitions is unusable, the optimizer can use table expansion. With table expansion, the optimizer transforms the query into a UNION ALLstatement, with some sub queries accessing indexed partitions and other sub queries accessing partitions with unusable indexes

Create the following partitioned table.

DROP TABLE test1 PURGE;

CREATE TABLE test1 (
  id            NUMBER,
  description   VARCHAR2(50),
  created_date  DATE
)
PARTITION BY RANGE (created_date) (
  PARTITION part_2014 VALUES LESS THAN (TO_DATE('01/01/2011', 'DD/MM/YYYY')) TABLESPACE users,
  PARTITION part_2015 VALUES LESS THAN (TO_DATE('01/01/2012', 'DD/MM/YYYY')) TABLESPACE users,
  PARTITION part_2016 VALUES LESS THAN (TO_DATE('01/01/2013', 'DD/MM/YYYY')) TABLESPACE users
);

INSERT INTO test1 VALUES (1, 'test1 ONE', TO_DATE('01/07/2011', 'DD/MM/YYYY'));
INSERT INTO test1 VALUES (2, 'test1 TWO', TO_DATE('01/07/2012', 'DD/MM/YYYY'));
INSERT INTO test1 VALUES (3, 'test1 THREE', TO_DATE('01/07/2013', 'DD/MM/YYYY'));
COMMIT;

Create a global index.

CREATE INDEX test1_idx1 ON test1(created_date) GLOBAL VISIBLE;

Index created.

SQL>

Create some indexes with differing partitioning schemes.

CREATE INDEX test1_idx2 ON test1(created_date) GLOBAL
PARTITION BY RANGE (created_date) (
  PARTITION test1_p1 VALUES LESS THAN (TO_DATE('01/01/2012', 'DD/MM/YYYY')) TABLESPACE users,
  PARTITION test1_p2 VALUES LESS THAN (TO_DATE('01/01/2013', 'DD/MM/YYYY')) TABLESPACE users,
  PARTITION test1_p3 VALUES LESS THAN (MAXVALUE) TABLESPACE users
)
INVISIBLE;

Index created.

SQL>


CREATE INDEX test1_idx3 ON test1(created_date) LOCAL INVISIBLE;

Index created.

SQL>

Create a bitmapped index.

CREATE BITMAP INDEX test1_idx4 ON test1(created_date) LOCAL INVISIBLE;

Index created.

SQL>

Why we are using Multiple Indexes

Invisible indexes are still maintained, so having multiple indexes on the same set of columns allows you to quickly switch between them, making testing the impact of various indexes much quicker. Remember, there is an impact on DML performance of having too many indexes on a table, so this should be a short term situation.

The following example used the partitioned table and the associated indexes created in the previous section.

-- Check visibility of indexes.
COLUMN index_name FORMAT A10
COLUMN index_type FORMAT A10
COLUMN partitioned FORMAT A12
COLUMN locality FORMAT A8
COLUMN visibility FORMAT A10

SELECT a.index_name,
       a.index_type,
       a.partitioned,
       b.partitioning_type,
       b.locality,
       a.visibility
FROM   user_indexes a
       LEFT OUTER JOIN user_part_indexes b ON a.index_name = b.index_name
ORDER BY index_name;

INDEX_NAME INDEX_TYPE PARTITIONED  PARTITION LOCALITY   VISIBILITY
---------- ---------- ------------ --------- ---------- ----------
test1_IDX1    NORMAL     NO                                VISIBLE
test1_IDX2    NORMAL     YES          RANGE     GLOBAL     INVISIBLE
test1_IDX3    NORMAL     YES          RANGE     LOCAL      INVISIBLE
test1_IDX4    BITMAP     YES          RANGE     LOCAL      INVISIBLE

SQL>


-- Test the index usage.
SET AUTOTRACE TRACE EXPLAIN

SELECT *
FROM   test1
WHERE created_date = TO_DATE('01/07/2014', 'DD/MM/YYYY');

----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                  | Name    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                           |         |     1 |    49 |     1   (0)| 00:00:01 |       |       |
|   1 |  TABLE ACCESS BY GLOBAL INDEX ROWID BATCHED| test1      |     1 |    49 |     1   (0)| 00:00:01 |     1 |     1 |
|*  2 |   INDEX RANGE SCAN                         | test1_IDX1 |     1 |       |     1   (0)| 00:00:01 |       |       |
----------------------------------------------------------------------------------------------------------------------

SET AUTOTRACE OFF

Switch the index visibility and test again.

-- Switch indexes.
ALTER INDEX test1_idx1 INVISIBLE;
ALTER INDEX test1_idx2 VISIBLE;


-- Check visibility of indexes.
SELECT a.index_name,
       a.index_type,
       a.partitioned,
       b.partitioning_type,
       b.locality,
       a.visibility
FROM   user_indexes a
       LEFT OUTER JOIN user_part_indexes b ON a.index_name = b.index_name
ORDER BY index_name;

INDEX_NAME INDEX_TYPE PARTITIONED  PARTITION LOCALITY   VISIBILITY
---------- ---------- ------------ --------- ---------- ----------
test1_IDX1    NORMAL     NO                                INVISIBLE
test1_IDX2    NORMAL     YES          RANGE     GLOBAL     VISIBLE
test1_IDX3    NORMAL     YES          RANGE     LOCAL      INVISIBLE
test1_IDX4    BITMAP     YES          RANGE     LOCAL      INVISIBLE

SQL>


-- Test the index usage.
SET AUTOTRACE TRACE EXPLAIN

SELECT *
FROM   test1
WHERE created_date = TO_DATE('01/07/2012', 'DD/MM/YYYY');

-----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
-----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                            |         |     1 |    49 |     1   (0)| 00:00:01 |       |       |
|   1 |  PARTITION RANGE SINGLE                     |         |     1 |    49 |     1   (0)| 00:00:01 |     1 |     1 |
|   2 |   TABLE ACCESS BY GLOBAL INDEX ROWID BATCHED| test1      |     1 |    49 |     1   (0)| 00:00:01 |     1 |     1 |
|*  3 |    INDEX RANGE SCAN                         | test1_IDX2 |     1 |       |     1   (0)| 00:00:01 |     1 |     1 |
-----------------------------------------------------------------------------------------------------------------------

SET AUTOTRACE OFF

Switch the index visibility once again and test.

-- Switch indexes.
ALTER INDEX test1_idx2 INVISIBLE;
ALTER INDEX test1_idx3 VISIBLE;


-- Check visibility of indexes.
SELECT a.index_name,
       a.index_type,
       a.partitioned,
       b.partitioning_type,
       b.locality,
       a.visibility
FROM   user_indexes a
       LEFT OUTER JOIN user_part_indexes b ON a.index_name = b.index_name
ORDER BY index_name;

INDEX_NAME INDEX_TYPE PARTITIONED  PARTITION LOCALITY   VISIBILITY
---------- ---------- ------------ --------- ---------- ----------
test1_IDX1    NORMAL     NO                                INVISIBLE
test1_IDX2    NORMAL     YES          RANGE     GLOBAL     INVISIBLE
test1_IDX3    NORMAL     YES          RANGE     LOCAL      VISIBLE
test1_IDX4    BITMAP     YES          RANGE     LOCAL      INVISIBLE

SQL>


-- Test the index usage.
SET AUTOTRACE TRACE EXPLAIN

SELECT *
FROM   test1
WHERE created_date = TO_DATE('01/07/2012', 'DD/MM/YYYY');

----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                  | Name    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                           |         |     1 |    49 |     1   (0)| 00:00:01 |       |       |
|   1 |  PARTITION RANGE SINGLE                    |         |     1 |    49 |     1   (0)| 00:00:01 |     1 |     1 |
|   2 |   TABLE ACCESS BY LOCAL INDEX ROWID BATCHED| test1      |     1 |    49 |     1   (0)| 00:00:01 |     1 |     1 |
|*  3 |    INDEX RANGE SCAN                        | test1_IDX3 |     1 |       |     1   (0)| 00:00:01 |     1 |     1 |
----------------------------------------------------------------------------------------------------------------------

SET AUTOTRACE OFF

Switch the index visibility once again and test.

-- Switch indexes.
ALTER INDEX test1_idx3 INVISIBLE;
ALTER INDEX test1_idx4 VISIBLE;


-- Check visibility of indexes.
SELECT a.index_name,
       a.index_type,
       a.partitioned,
       b.partitioning_type,
       b.locality,
       a.visibility
FROM   user_indexes a
       LEFT OUTER JOIN user_part_indexes b ON a.index_name = b.index_name
ORDER BY index_name;

INDEX_NAME INDEX_TYPE PARTITIONED  PARTITION LOCALITY   VISIBILITY
---------- ---------- ------------ --------- ---------- ----------
test1_IDX1    NORMAL     NO                                INVISIBLE
test1_IDX2    NORMAL     YES          RANGE     GLOBAL     INVISIBLE
test1_IDX3    NORMAL     YES          RANGE     LOCAL      INVISIBLE
test1_IDX4    BITMAP     YES          RANGE     LOCAL      VISIBLE

SQL>


-- Test the index usage.
SET AUTOTRACE TRACE EXPLAIN

SELECT *
FROM   test1
WHERE created_date = TO_DATE('01/07/2012', 'DD/MM/YYYY');

----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                  | Name    | Rows  | Bytes | Cost (%CPU)| Time     | Pstart| Pstop |
----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                           |         |     1 |    49 |    15   (0)| 00:00:01 |       |       |
|   1 |  PARTITION RANGE SINGLE                    |         |     1 |    49 |    15   (0)| 00:00:01 |     1 |     1 |
|   2 |   TABLE ACCESS BY LOCAL INDEX ROWID BATCHED| test1      |     1 |    49 |    15   (0)| 00:00:01 |     1 |     1 |
|   3 |    BITMAP CONVERSION TO ROWIDS             |         |       |       |            |          |       |       |
|*  4 |     BITMAP INDEX SINGLE VALUE              | test1_IDX4 |       |       |            |          |     1 |     1 |
----------------------------------------------------------------------------------------------------------------------

SET AUTOTRACE OFF    detail information of index here

Indexes Data Dictionary Views

The following views display information about indexes:

The post Multiple Indexes in Oracle Database 12c appeared first on Oracle for All.

Tables Data Dictionary Views

The following views allow you to access information about tables.

Example: Displaying Column Information

Column information, such as name, datatype, length, precision, scale, and default data values can be listed using one of the views ending with the _COLUMNS suffix. For example, the following query lists all of the default column values for the emp and dept tables:

SELECT TABLE_NAME, COLUMN_NAME, DATA_TYPE, DATA_LENGTH, LAST_ANALYZED
    FROM DBA_TAB_COLUMNS
    WHERE OWNER = 'HR'
    ORDER BY TABLE_NAME;
    

The following is the output from the query:

TABLE_NAME           COLUMN_NAME          DATA_TYPE   DATA_LENGTH LAST_ANALYZED
-------------------- -------------------- ---------- ------------ -------------
COUNTRIES            COUNTRY_ID           CHAR                  2 05-FEB-03
COUNTRIES            COUNTRY_NAME         VARCHAR2             40 05-FEB-03
COUNTRIES            REGION_ID            NUMBER               22 05-FEB-03
DEPARTMENTS          DEPARTMENT_ID        NUMBER               22 05-FEB-03
DEPARTMENTS          DEPARTMENT_NAME      VARCHAR2             30 05-FEB-03
DEPARTMENTS          MANAGER_ID           NUMBER               22 05-FEB-03
DEPARTMENTS          LOCATION_ID          NUMBER               22 05-FEB-03
EMPLOYEES            EMPLOYEE_ID          NUMBER               22 05-FEB-03
EMPLOYEES            FIRST_NAME           VARCHAR2             20 05-FEB-03
EMPLOYEES            LAST_NAME            VARCHAR2             25 05-FEB-03
EMPLOYEES            EMAIL                VARCHAR2             25 05-FEB-03
.
.
.
LOCATIONS            COUNTRY_ID           CHAR                  2 05-FEB-03
REGIONS              REGION_ID            NUMBER               22 05-FEB-03
REGIONS              REGION_NAME          VARCHAR2             25 05-FEB-03

The post Most important table for DBA appeared first on Oracle for All.

Indexes are optional structures associated with tables and clusters that allow SQL queries to execute more quickly against a table. Just as the index in this manual helps you locate information faster than if there were no index, an Oracle Database index provides a faster access path to table data. You can use indexes without rewriting any queries. Your results are the same, but you see them more quickly.

The post Indexes most important tables and views appeared first on Oracle for All.