Article / Updated 03-26-2016
When your data is in more than one place, you need ways to put it all together. When you join two datasets with different variables, you’re merging data. Merging is a common operation. Merging is used frequently in data mining, combining linked data such as
Customer records and marketing campaign data
Before and after test results
Internal and vendor data
To merge datasets, you must have a variable that identifies cases for matching; this is called a key or identifier variable.