Both GROUP and COGROUP operators are identical and can work with one or more relations. GROUP operator is generally used to group the data in a single relation for better readability, whereas COGROUP can be used to group the data in 2 or more relations. COGROUP is more like a combination of GROUP and JOIN, i.e., it groups the tables based on a column and then joins them on the grouped columns. It is possible to cogroup up to 127 relations at a time.
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