MySQL Update and delete

Update and DELETE operations SQL statements are simpler, but note that when you use update, pay attention to the limitations of weher conditions, the following statement is only update ID 10005 email address, if not the where statement restrictions, then the table all of the email update to Elmer@fudd.com:

Delete the value of a column, set to NULL.

Deletes the SQL statement for the row, using the Delete, which also deletes the row you want to delete, or deletes all rows in the table if you do not specify it.

DELETE from Customers

WHERE cust_id = 10005;

So far we see the importance of the primary key in a table. In addition, before the update and delete, you can use the SELECT statement to test whether the condition defined by the WHERE statement is correct.