The DELETE statement is used to delete rows from an Oracle table. Syntax: DELETE FROM table_name [WHERE condition]; DELETE can delete all rows, delete rows based on conditions, or use subqueries to delete rows; note that DELETE cannot be undone, please back up the data before execution, and it may take a long time to complete for large tables operate.
DELETE statement in Oracle
What is the DELETE statement?
The DELETE statement is used to delete rows from an Oracle table.
Syntax:
<code>DELETE FROM table_name [WHERE condition];</code>
Where:
-
table_name: The name of the table from which rows are to be deleted. -
WHERE condition(optional): Condition clause used to specify which rows to delete.
How to use DELETE statement?
- Delete all rows:
<code>DELETE FROM table_name;</code>
- Delete rows based on conditions:
<code>DELETE FROM table_name WHERE condition;</code>
For example, to delete all rows with a salary less than 10,000 from the employees table, you can use the following statement:
<code>DELETE FROM employees WHERE salary < 10000;</code>
- Delete using a subquery Rows:
The DELETE statement can be used with a subquery to delete rows based on conditions in other tables. For example, to delete orders from the orders table that do not have any shipped status, you would use the following statement:
<code>DELETE FROM orders WHERE order_status NOT IN (SELECT order_status FROM order_statuses WHERE is_shipped = 1);</code>
Note:
- DELETE statement cannot be undone. Before executing a DELETE statement, make sure you have backed up your data.
- If the WHERE clause is not specified, the DELETE statement will delete all rows in the table.
- For larger tables, the DELETE operation may take a lot of time.
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