Updating and Deleting Data - MariaDB Crash Course - page 167

Tip
The IGNORE Keyword If your UPDATE statement updates multiple rows and an
error occurs while updating one or more of those rows, the entire UPDATE operation is
cancelled (and any rows updated before the error occurred are restored to their original
values). To continue processing updates, even if an error occurs, use the IGNORE key-
word, like this:
UPDATE IGNORE customers ...

To delete a column's value, you can set it to NULL (assuming the table is
defined to allow NULL values). You can do this as follows:

▼ Input
UPDATE customers
SET cust_email = NULL
WHERE cust_id = 10005;

Here the NULL keyword is used to save no value to the cust_email column.

Deleting Data
To delete (remove) data from a table, the DELETE statement is used. DELETE

can be used in two ways:

To delete specific rows from a table

■

To delete all rows from a table

■

We now take a look at each of these.

Caution
Don't Omit the WHERE Clause Special care must be exercised when using DELETE
because it is all too easy to mistakenly delete every row from your table. Please read
this entire section on DELETE before using this statement.

Tip
DELETE and Security Use of the DELETE statement can be restricted and con-
trolled. More on this in Chapter 28.

I already stated that UPDATE is easy to use. The good (and bad) news is that
DELETE is even easier to use.
The following statement deletes a single row from the customers table: