Questions 4.1. How do the relations (tables) in SQL differ from the relations defined formally in Chapter 3? Discuss the other differences in terminology. Why does SQL allow duplicate tuples in a table or in a query result?
Solution: SQL allows a table to have more than one tuple that are identical in all their attribute values while others don't
The reasons why SQL allows duplicate tuples are
- Duplicate elimination is an expensive operation
- User may want to see duplicate tuples in the result of query
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