Step-by-Step Programming with Base SAS 9.4

Definition of Modifying

Modifying a SAS data set replaces, deletes, or appends observations in an existing data set. Modifying a SAS data set is similar to updating a SAS data set, but the following differences exist:

• Modifying cannot create a new data set, but updating can.
• Unlike updating, modifying does not require that the master data set or the transaction data set be sorted.

You use a MODIFY statement along with a BY statement to change an existing data set.

In the following example, the MASTER data set is updated by YEAR.

Figure 16.6 Modifying a Data Set

Notice that the TRANSACTION data set contains missing values. When ...