What is the difference between executing the TRUNCATE command and using the DELETE command when clearing a table?

The TRUNCATE and DELETE commands are both used to remove data from a table, but they have significant differences:

• TRUNCATE:

  • A fast operation that removes all rows from the table entirely.
  • Usually operates without logging the deletion of each row, which speeds up the process.
  • Does not invoke DELETE triggers.
  • Does not allow the use of WHERE — it deletes all data.
  • Can reset auto-increment counters.
  • Restoring data after TRUNCATE is more difficult, as the operation is often not logged row-by-row.

• DELETE:

  • Removes rows based on a condition (if WHERE is specified), or all rows if WHERE is absent.
  • Logs the deletion of each row, which can be slower.
  • Invokes DELETE triggers.
  • Allows more flexible data removal.

Example:

-- Quickly delete all records from a table
TRUNCATE TABLE employees;

-- Delete only employees from the 'Sales' department
DELETE FROM employees WHERE department = 'Sales';

Thus, TRUNCATE is suitable for quickly clearing an entire table, while DELETE is used for selective removal.