Unformatted text preview: equivalence rules 2. Annotate resultant expressions to get alternative query plans 3. Choose the cheapest plan based on estimated cost Two relational algebra expressions are said to be equivalent if the two expressions generate the same set of tuples on every legal database instance. Note: the order of tuples is irrelevant. Read the equivalence rules on slide 14.8 – 14.13. Rule 7b is very important and is likely to be on the test....
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- Fall '08
- Databases, Relational model, relational algebra expression, relational algebra expressions, logically equivalent expressions, Annotate resultant expressions