Plz tell me why is merge sort called external sort and what is the tree sort .Questions have been asked on the quiz .
Sorting techniques
The sorting of relations which do not fit in the memory because their size is larger than the memory size. Such type of sorting is known as External Sorting
One example of external sorting is the external merge sort algorithm, which sorts chunks that each fit in RAM, then merges the sorted chunks together. We first divide the file into runs such that the size of a run is small enough to fit into main memory. Then sort each run in main memory using merge sort sorting algorithm. Finally merge the resulting runs together into successively bigger runs, until the file is sorted.
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