How to delete all user tables in oracle

Oracle is currently the most popular relational database management system in the world. However, when a user needs to be deleted, all tables of the user may be deleted. Following are some methods to delete user-owned tables in Oracle.

1. Use the DROP USER command

Use the DROP USER command to delete the user and all tables and objects owned by the user. However, this command is only suitable for situations where users and their objects need to be completely deleted, and may cause severe data loss.

The syntax for using the DROP USER command is as follows:

DROP USER username CASCADE;

where username is the name of the user to be deleted. Using the CASCADE keyword will delete all user objects, including tables, indexes, constraints, views, etc.

It should be noted that before using this command, you need to be very sure whether you want to delete the user and its objects. If no measures are taken to back up or ensure data reliability, this will result in irreversible data loss.

2. Use PL/SQL scripts

Using PL/SQL scripts can help control which tables are deleted in a more fine-grained manner. The following is an example:

DECLARE
      l_sql VARCHAR2(1000);
BEGIN
      FOR t IN (SELECT table_name FROM user_tables)
      LOOP
          l_sql := 'DROP TABLE ' || t.table_name;
          EXECUTE IMMEDIATE l_sql;
      END LOOP;
END;

The script iterates through all the user's tables and uses the EXECUTE IMMEDIATE command to execute the statement that deletes the table. Use this method to delete each table of a user individually.

It should be noted that when using scripts to perform deletion operations, please be careful to ensure that only the tables that need to be deleted are deleted to avoid accidentally deleting other tables.

3. Use the DBMS_METADATA.GET_GRANTED_DDL function

You can use the DBMS_METADATA.GET_GRANTED_DDL function to obtain the DDL statements of the specified user and all objects owned by it. You can extract the required CREATE TABLE statements from it and then drop the tables manually.

The following is an example:

SELECT
       DBMS_METADATA.GET_GRANTED_DDL('TABLE', USERNAME) AS GRANT_STMT
FROM
        ALL_USERS;

This statement will return the CREATE TABLE statement. You can then copy-paste these statements into a new SQL editor and manually delete the tables one by one.

It should be noted that this method will return DDL statements for all tables and objects owned by this user, so you will need to extract and delete the required tables from it according to your needs.

Summary

Deleting users and their tables in Oracle requires great caution. Using the DROP USER command will delete the user and all its objects at the same time, which may result in data loss. More fine-grained control can be achieved using PL/SQL scripts or the DBMS_METADATA.GET_GRANTED_DDL function, but caution is required. Before performing a deletion operation, be sure to make backups or take measures to ensure data reliability to avoid irreversible data loss.

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