The Sort Operation
Sorting is explicit in queries only in the order by clause
select * from Students order by name;
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Sorting is used internally in other operations:
- eliminating duplicate tuples for projection
- ordering files to enhance select efficiency
- implementing various styles of join
- forming tuple groups in
group by
Sort methods such as quicksort are designed for in-memory data.
For large data on disks, need external sorts such as merge sort.
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