UPDATE & DELETE

UPDATE table SET column = value WHERE condition changes existing rows. DELETE FROM table WHERE condition removes rows the same way.

Example: updating one specific row

UPDATE students SET score = 95 WHERE name = 'Chidi';

1 row updated.

The WHERE clause here isn't optional in practice, even though it's technically optional in syntax — leaving it off updates every single row in the table, not just the one you meant. This is one of the most common, most damaging mistakes anyone makes with SQL, and it's worth developing the habit of writing and double-checking your WHERE clause before you even glance at the SET or the rest of the statement. The exact same warning applies to DELETE, with even less room for a second chance.