SQL DELETE Statement

The DELETE statement in SQL is used to delete existing records in a table.

It is a powerful command that should be used with caution, as it permanently removes data from the table and can't be undone.

Syntax

The basic syntax for the DELETE statement is as follows:

DELETE FROM table_name WHERE some_column = some_value;
  • DELETE FROM is the keyword that tells the database to delete data.
  • table_name is the name of the table from which you want to delete data.
  • WHERE is used to specify the conditions for the deletion. The statement will only delete records that meet the specified condition.
  • some_column and some_value are used to specify the condition for the deletion. In this example, the statement will delete all records where the value of some_column is equal to some_value.

Examples

Delete all records from a table:

DELETE FROM customers;

Delete specific records from a table:

DELETE FROM customers WHERE customer_id = 2;

Delete records based on multiple conditions:

DELETE FROM customers WHERE city = 'Los Angeles' AND country = 'USA';

Delete all records from multiple tables:

DELETE FROM customers, orders WHERE customers.customer_id = orders.customer_id;

Caveats

  • Be careful when using the DELETE statement, as it permanently removes data from the table and can't be undone.
  • If you don't include a WHERE clause, the DELETE statement will delete all records in the table, which can be very dangerous.
  • It's a good practice to always include a WHERE clause in your DELETE statement to avoid accidentally deleting all records.
  • Before perform any delete statement, it's a good practice to make a backup copy of the table.
  • When deleting a record from a table that has a foreign key constraint, you must also delete the related records from the table that the foreign key references.

Remember to always include a WHERE clause in your DELETE statement to avoid accidentally deleting all records.

Additionally, it's a good practice to make a backup copy of the table before perform any delete statement.

SQL Basics