SQL: Structured Query Language - Oracle 10g Database Administration Concepts and Implementation Made Simple - page 45

sign (+) with the column of the table having least number of
records, in the WHERE clause.
I would like to have your focus on the NULL (empty) values in
the Figure 2-11; the one shown in the output table. These order
dates are NULL because there were no supplier ids 10002 &
10003 in the orders table.
UPDATE, INSERT & DELETE Statements
UPDATE statement is used to edit the information already
existing in the table. If you want to insert a new record in the
table then we use the INSERT statement and if you want to
delete any record or more than one record we use the DELETE
statement.
Figure 2-12: Other DML Statements. If you forget to mention the
WHERE clause in the UPDATE statement, all the values in that
column will get update. While inserting new values in the table the
order of columns should be kept in mind otherwise you may get a type
mismatch error.