Got it, let's tackle this problem step by step. Since your ADDRESS table is referenced by foreign keys in other tables (like CUSTOMERS) and you didn't set ON DELETE CASCADE when creating those constraints, you have a couple of reliable approaches to delete all ADDRESS records along with their dependent data.

Step 1: Identify All Tables Referencing ADDRESS #

First, you need to know exactly which tables have foreign keys pointing to ADDRESS. Run this query to get the full list:

SELECT 
    c.table_name AS referencing_table,
    cc.column_name AS referencing_column,
    c.constraint_name AS fk_constraint_name
FROM 
    user_constraints c
JOIN 
    user_cons_columns cc ON c.constraint_name = cc.constraint_name
WHERE 
    c.r_constraint_name IN (
        SELECT constraint_name 
        FROM user_constraints 
        WHERE table_name = 'ADDRESS' AND constraint_type = 'P'
    )
    AND c.constraint_type = 'R';

This will return every table, foreign key column, and constraint name linked to ADDRESS's primary key.

Approach 1: Temporarily Add ON DELETE CASCADE to Foreign Keys #

If you want Oracle to handle cascading deletes automatically (and optionally revert the constraint later), follow these steps:

1. Drop existing foreign key constraints (replace placeholders with your actual values from the above query):

   -- Example for Customers table
   ALTER TABLE CUSTOMERS DROP CONSTRAINT FK_CUSTOMERS_ADDRESS;
   

   Repeat this for every referencing table.

2. Recreate constraints with ON DELETE CASCADE:

   ALTER TABLE CUSTOMERS ADD CONSTRAINT FK_CUSTOMERS_ADDRESS 
   FOREIGN KEY (ADDRESS_ID) REFERENCES ADDRESS(ID) ON DELETE CASCADE;
   

   Again, repeat for all referencing tables.

3. Delete all data from ADDRESS:

   DELETE FROM ADDRESS;
   COMMIT;
   

   Oracle will automatically delete all dependent records in the referencing tables.

4. Optional: Revert constraints to original state (if you don't want ON DELETE CASCADE long-term):
   Drop the new constraints and recreate them without the ON DELETE CASCADE clause.

Approach 2: Manually Delete Dependent Records First #

If you prefer not to modify constraints (e.g., in a production environment with strict change control), manually delete dependent data before removing ADDRESS records:

1. Delete records from each referencing table:
   Use either an IN clause or EXISTS for better performance with large datasets:

   -- Option 1: Using IN
   DELETE FROM CUSTOMERS WHERE ADDRESS_ID IN (SELECT ID FROM ADDRESS);
   
   -- Option 2: Using EXISTS (more efficient for large tables)
   DELETE FROM CUSTOMERS c
   WHERE EXISTS (SELECT 1 FROM ADDRESS a WHERE a.ID = c.ADDRESS_ID);
   

   Repeat this for every table that references ADDRESS.

2. Delete all data from ADDRESS:

   DELETE FROM ADDRESS;
   COMMIT;
   

3. Optional: Wrap in a transaction to ensure atomicity (if one step fails, everything rolls back):

   BEGIN
       -- Delete from first referencing table
       DELETE FROM CUSTOMERS WHERE ADDRESS_ID IN (SELECT ID FROM ADDRESS);
       -- Add more DELETE statements for other referencing tables here
       -- DELETE FROM ORDERS WHERE SHIP_ADDRESS_ID IN (SELECT ID FROM ADDRESS);
       
       -- Finally delete from Address
       DELETE FROM ADDRESS;
       
       COMMIT;
   EXCEPTION
       WHEN OTHERS THEN
           ROLLBACK;
           RAISE; -- Re-throw the error to see what went wrong
   END;
   /
   

Critical Notes Before You Start #

• Backup your data: Always take a backup of ADDRESS and all referencing tables before performing mass deletes—you can't undo this easily.
• Test in a non-production environment: Validate these steps in a staging environment first to avoid unexpected issues.
• Check for locks: Modifying constraints or deleting large datasets can lock tables, so run these operations during low-traffic periods.
• Permissions: Ensure you have DELETE privileges on all affected tables, and ALTER TABLE privileges if using Approach 1.

内容的提问来源于stack exchange，提问作者Awadesh