A SQL Delete Statement
The SQL DELETE statement is used to remove one or more rows from a database table based on a specified condition. It permits the deletion of data from a table while preserving the table structure.
When you delete the exiting records in a table, please be careful, but you must use the where clause otherwise, all records will get deleted without the where clause.
Here is the syntax of the delete statement:
SQL> DELETE FROM table_name
WHERE condition;
Let’s break down this syntax with some examples:
SQL DELETE with examples
Example 1: Deleting a Single Record
Suppose you have a table called customers with columns customer_id, first_name, and last_name, and you want to delete the record of a customer with customer_id equal to 121.
SQL> DELETE FROM customers
WHERE customer_id = 121;
This SQL statement will remove the entire row of data for the customer with customer_id 121 from the customers table.
Example 2: Deleting Multiple Records
SQL> DELETE FROM products
WHERE quantity = 0;
This SQL statement deletes all rows from the products table where the quantity column equals 0.
Example 3: Deleting All Rows
The DELETE command will delete every row in the table if the WHERE clause is left off, effectively emptying the table. Because it permanently deletes all of the table’s data, use this command with caution.
SQL> DELETE FROM employees;
This SQL statement would delete all rows from the employees table.
Always be careful when using delete statements because they can result in permanent data loss, especially when used without a WHERE clause.
NOTE: To prevent unintended data removal, always double-check your conditions and make sure you’re deleting the intended data before executing the DELETE statement. To secure data recovery in the event of a need, think about creating backups of your data before undertaking mass deletions.