SQL scripts for Indexes and Index-Organized Tables (IOTs), along with sample output, description, and SQL queries

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1. List the Indexes Associated with an Index-Organized Table 

This script lists the indexes associated with a specific Index-Organized Table (IOT). Replace 'YOUR_IOT_TABLE_NAME' with the name of the IOT for which you want to view the associated indexes. The script queries the all_ind_columns data dictionary view to retrieve index information for the specified IOT.

-- Query to list the indexes associated with an Index-Organized Table
SELECT table_name, index_name, uniqueness, column_name
FROM all_ind_columns
WHERE table_name = 'YOUR_IOT_TABLE_NAME';

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Sample output

TABLE_NAME     INDEX_NAME      UNIQUENESS    COLUMN_NAME
-------------  -------------   ------------  -------------
EMPLOYEES_IOT  EMPLOYEES_PK    UNIQUE        EMPLOYEE_ID
EMPLOYEES_IOT  EMPLOYEES_NAME  NONUNIQUE     EMPLOYEE_NAME

2. Analyze the Performance of Index Access on an IOT This script analyzes the performance of index access on an Index-Organized Table (IOT) for a specific query. Replace 'YOUR_IOT_TABLE_NAME' with the name of the IOT you want to analyze, and 'YOUR_CONDITIONS' with the conditions you want to evaluate. The script generates the execution plan for the query using the EXPLAIN PLAN FOR statement and displays it using DBMS_XPLAN.DISPLAY. This helps you understand how the query accesses the index on the IOT.

 

-- Query to analyze the performance of index access on an IOT
EXPLAIN PLAN FOR
SELECT * FROM YOUR_IOT_TABLE_NAME WHERE YOUR_CONDITIONS;

SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);

Sample output

PLAN_TABLE_OUTPUT
-------------------------------------------------------------
Plan hash value: 1234567890
 
-----------------------------------------------------------
| Id  | Operation           | Name           | Rows  | Cost |
-----------------------------------------------------------
|   0 | SELECT STATEMENT    |                |   100 |  2   |
|   1 |  TABLE ACCESS BY ROWID  | YOUR_IOT_TABLE |   100 |  2   |
|   2 |   INDEX UNIQUE SCAN     | YOUR_IOT_PK    |   100 |  1   |
-----------------------------------------------------------

3. Rebuild or Reorganize an Index on an IOT 

These scripts rebuild and reorganize an index on an Index-Organized Table (IOT) for performance optimization. Replace 'YOUR_IOT_INDEX_NAME' with the name of the index on the IOT you want to rebuild or reorganize. The ALTER INDEX ... REBUILD statement rebuilds the index entirely, reclaiming space and defragmenting the index structure. The ALTER INDEX ... REORGANIZE statement reorganizes the index by compacting it and improving its performance.

-- Query to rebuild an index on an IOT
ALTER INDEX YOUR_IOT_INDEX_NAME REBUILD;

-- Query to reorganize an index on an IOT
ALTER INDEX YOUR_IOT_INDEX_NAME REORGANIZE;

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