2026-03-12 20:23:15

idev/example_drop_unused_column.sql

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+-- +----------------------------------------------------------------------------+
+-- |                          Jeffrey M. Hunter                                 |
+-- |                      jhunter@idevelopment.info                             |
+-- |                         www.idevelopment.info                              |
+-- |----------------------------------------------------------------------------|
+-- |      Copyright (c) 1998-2012 Jeffrey M. Hunter. All rights reserved.       |
+-- |----------------------------------------------------------------------------|
+-- | DATABASE : Oracle                                                          |
+-- | FILE     : example_drop_unused_column.sql                                  |
+-- | CLASS    : Examples                                                        |
+-- | PURPOSE  : Example SQL syntax used to drop unused columns from a table.    |
+-- | NOTE     : As with any code, ensure to test this script in a development   |
+-- |            environment before attempting to run it in production.          |
+-- +----------------------------------------------------------------------------+
+
+connect scott/tiger
+
+set serveroutput on
+
+Prompt ======================
+Prompt DROP existing table...
+Prompt ======================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+DROP TABLE d_table
+/
+
+
+Prompt =======================
+Prompt CREATE TESTING TABLE...
+Prompt =======================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+CREATE TABLE d_table (
+    id_no     NUMBER
+  , name      VARCHAR2(100)
+  , d_column  VARCHAR2(100)
+)
+/
+
+
+Prompt ========================
+Prompt MARK COLUMN AS UNUSED...
+Prompt ========================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+ALTER TABLE d_table SET UNUSED COLUMN d_column;
+
+
+Prompt =======================================
+Prompt QUERY ALL TABLES WITH UNUSED COLUMNS...
+Prompt =======================================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+SELECT * FROM sys.dba_unused_col_tabs;
+
+
+Prompt ======================================
+Prompt PHYSICALLY REMOVE THE UNUSED COLUMN...
+Prompt ======================================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+ALTER TABLE d_table DROP UNUSED COLUMNS;
+
+
+Prompt ================================================
+Prompt IF YOU WANTED TO PHYSICALLY REMOVE THE COLUMN...
+Prompt ================================================
+Prompt
+accept a1 Prompt "Hit <ENTER> to continue";
+
+-- ALTER TABLE d_table DROP COLUMN d_column;
+
+
+Prompt =========================================
+Prompt OPTIONALLY SYNTAX FOR REMOVING COLUMNS...
+Prompt =========================================
+Prompt
+Prompt ALTER TABLE d_table DROP COLUMN d_column CASCADE CONSTRAINTS;
+Prompt ALTER TABLE d_table DROP COLUMN d_column INVALIDATE;
+Prompt ALTER TABLE d_table DROP COLUMN d_column CHECKPOINT 1000;
+Prompt
+accept a1 Prompt "Hit <ENTER> to EXIT";
+
+