Delete usage in oracle

The DELETE statement deletes data from the Oracle database through the "DELETE FROM table_name WHERE condition;" syntax. It can specify conditions to conditionally delete rows (for example, salary is less than 5000). Advanced uses include TRUNCATE TABLE (quickly deletes all data), CASCADE DELETE (cascade deletes related data), and WHERE CURRENT OF (deletes the current row from the cursor). To avoid accidental deletions, be sure to use conditions and consider using indexes on large amounts of data to improve performance.

DELETE statement in Oracle

Purpose of DELETE statement:

DELETE statement is used to delete one or more rows of data from the Oracle database.

Syntax:

<code class="sql">DELETE FROM table_name
WHERE condition;</code>

Parameters:

• table_name: To delete data from table name.
• condition: Optional condition used to specify rows of data to be deleted. If no condition is specified, all rows in the table will be deleted.

Usage example:

To delete all employees whose salary is less than 5000 from the "employees" table, you can use the following statement:

<code class="sql">DELETE FROM employees
WHERE salary < 5000;</code>

Advanced Usage:

• TRUNCATE TABLE: The TRUNCATE TABLE statement is an alternative to quickly deleting all data in a table. It is faster than the DELETE statement and does not generate an undo log, but it cannot conditionally delete data.
• CASCADE DELETE: When using the DELETE statement on a table with foreign key constraints, you can specify CASCADE DELETE to cascade delete data in the related table.
• WHERE CURRENT OF: Can be used to delete the current row from the cursor.

Note:

• DELETE statement cannot be undone. Always ensure that the correct data is deleted before executing a DELETE statement.
• The best practice is to use conditions to limit deleted data to avoid accidental deletion.
• When executing DELETE statements on large amounts of data, you should consider using indexes to improve performance.

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