Deleting Data and Tables in SQL: A Comprehensive Guide

Deleting Records with DELETE

The DELETE statement allows you to remove specific records from a table based on specified criteria. This is useful when you want to delete certain rows without affecting the entire table.

DELETE FROM table_name WHERE condition;

Dropping Tables with DROP TABLE

The DROP TABLE statement removes an entire table from the database. This is a permanent action, so proceed with caution. Be aware that if the table is referenced by other tables through foreign key constraints, you may need to drop those tables first.

DROP TABLE table_name;

Choosing Between DELETE and TRUNCATE TABLE

When deleting all data from a table, you can choose between the DELETE and TRUNCATE TABLE statements. DELETE removes each row individually, while TRUNCATE TABLE instantly removes all data without logging any changes. TRUNCATE TABLE is faster but cannot be rolled back.

DELETE FROM table_name; TRUNCATE TABLE table_name;

Handling Foreign Key Constraints

If you try to drop a table that is referenced by a foreign key constraint, you will encounter an error. To drop such a table, you can either delete the referencing rows first or drop the foreign key constraint.

ALTER TABLE table_name DROP FOREIGN KEY constraint_name; DELETE FROM referencing_table WHERE column_name IN (SELECT column_name FROM table_name);