Modern database systems use a query optimizer to identify query plan to execute declarative SQL queries. Optimization is a mandatory exercise since the difference between the cost of the best plan and a random choice could be in orders of magnitude. The role of query optimizers is especially critical for the decision-support queries featured in data warehousing and data mining applications. For a query on a given database and system configuration, the optimizer¿s plan choice is primarily a function of the selectivities of the base relations participating in the query. In this chapter, it has been projected towards the cost of sub-query operations on the various sites, as well as the benefits achieved in the range of thirty to forty percent for various sub-operations like selection, projection and join.
| Autorius: | Sambit Kumar Mishra |
| Leidėjas: | LAP LAMBERT Academic Publishing |
| Išleidimo metai: | 2017 |
| Knygos puslapių skaičius: | 52 |
| ISBN-10: | 3330079266 |
| ISBN-13: | 9783330079267 |
| Formatas: | Knyga minkštu viršeliu |
| Kalba: | Anglų |
| Žanras: | Careers guidance |
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