Database Reference
In-Depth Information
20
In this chapter, you learn how to use the
UPDATE
and
DELETE
statements to
enable you to further manipulate your table data.
To update (modify) data in a table the
UPDATE
statement is used.
UPDATE
can
be used in two ways:
To update specific rows in a table
■
To update all rows in a table
■
Let's take a look at each of these uses.
Caution
Don't Omit the
WHERE
Clause Special care must be exercised when using
UPDATE
because it is all too easy to mistakenly update every row in your table. Please read this
entire section on
UPDATE
before using this statement.
Tip
UPDATE
and Security Use of the
UPDATE
statement can be restricted and con-
trolled. More on this in Chapter 28, “Managing Security.”
The
UPDATE
statement is easy to use—some would say too easy. The basic
format of an
UPDATE
statement is made up of three parts:
The table to be updated
■
The column names and their new values
■
The filter condition that determines which rows should be updated
■
