Differences Between MERGE and APPEND Procedures in SAS

When working with data in SAS, it is important to understand the differences between the MERGE and APPEND procedures.

MERGE Procedure:

• MERGE is used to combine two or more datasets by matching the values of specified variables.
• It creates a new dataset by merging the observations of the input datasets based on the values of the key variables.
• When using the MERGE procedure, the input datasets must be sorted by the key variables.
• Commonly used when you need to combine datasets with a one-to-one or one-to-many relationship.

APPEND Procedure:

• APPEND is used to vertically stack datasets, adding observations from one dataset to another.
• It does not require the datasets to be sorted and simply appends one dataset to another.
• When using the APPEND procedure, the variables in the datasets must match in number and type.
• Commonly used when you need to simply stack datasets without any matching criteria.

Choosing Between MERGE and APPEND:

The choice between using the MERGE and APPEND procedures in SAS depends on the specific data manipulation requirements:

• Use MERGE when you need to combine datasets based on specific key variables and maintain the relationship between observations.
• Use APPEND when you only need to stack datasets vertically without any matching criteria.