To update record or data DELETE query is used.
Syntax:
DELETE FROM table_name WHERE condition;
First show all data from contact table:
SELECT * FROM contact;

DELETE data where id = 14:
DELETE FROM contact WHERE id = 14;

After deleting again show all data from contact table:
SELECT * FROM contact;

DELETE all data from table:
Syntax:
DELETE FROM table_name;
Be care fully about delete query. You can't restore data.