The most effective method to union distinctive dataset values in SAS utilizing Merge concept

A SAS dataset is structure file that contains columns and rows. These columns and rows are used to store the data; the data that is stored in the SAS environment is stored in the form of tabular structure, this table which contains data within it is called as a dataset. Sometime to manage these datasets together, programmer has to join these datasets together into a single dataset.

To merge these datasets merging concept is used. The basic idea of this merge is to combine the values/contents of two or more datasets that contain different variables and might have nearly the same number of observations.

There are two types of merging:
One - to - one merging and match merging. In one - to - one merging, merge statement do not require a BY statement. Observations are combined based on their positions in the input data sets. Where as in match merging, merge statement need a BY statement to combine observations from the input data sets based on common values of the variable.

Syntax to Merge

MERGE SAS-data-set-list;
BY variable-list;

SAS-data-set-list: is the names of two or more SAS data sets to merge. The list may contain any number of data sets.
 
variable-list: is one or more variables by which to merge the data sets. If a BY statement is used, then the data sets must be sorted by the same BY variables before merging the data sets.

Different types of merging:

One-to-One Merging: 
In one-to-one merge, the number of observations in the new data set is equal to the number of observations in the largest data set named in the MERGE statement.

Match-Merging:
Merging with a BY statement enables to match observations according to the values of the BY variables that specified. Before performing a match-merge, all data sets must be sorted by the variables that is used for merging.

In order to understand match-merging, there are three key concepts:

BY variable - is a variable named in a BY statement.
BY value - is the value of a BY variable.
BY group - is the set of all observations with the same value for the BY variable (if there is only one BY variable).

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