Methods of Combining SAS Data Sets

Comparing Modifying, Merging, and Updating Data Sets

The table that follows summarizes several differences among the MERGE, UPDATE, and MODIFY statements.

Criterion	MERGE	UPDATE	MODIFY
Data sets must be sorted or indexed	Match-merge: Yes One-to-one merge: No	Yes	No
BY values must be unique	No	Master data set: Yes Transaction data set: No	No
Can create or delete variables	Yes	Yes	No
Number of data sets combined	Any number	2	2
Processing missing values	Overwrites nonmissing values from first data set with missing values from second data set	Default behavior: missing values in the transaction data set do not replace values in the master data set	Depends on the value of the UPDATEMODE= option (see Comparing Modifying, Merging, and Updating Data Sets) Default: MISSINGCHECK