Relational theory does not address indexes

Post #212,197 by tablizer 6/22/05 11:10:09 PM Reply	Relational theory does not address indexes as far as I know. Indexes are just an implementation (speed) aide. In theory one should get the same result rows from any given query regardless of whether indexes are in place or not. But, it appears an index of some kind is necessary in order to efficiently enforce the primary key constraint required by the theory. ________________ oop.ismad.com
Post #212,202 by ChrisR 6/22/05 11:24:01 PM Reply	Indexes are just tables.... ...with the last field being a pointer to the record with the corresponding row in the full table. If the Index has full coverage, the query optimizer can get all the data from the index and never have to look at the full table. The primary reason for efficiency is due to have all the records in near vicinity to each other and in the correct order (as opposed to having to check every record scattered throughout the storage unit).
Post #212,260 by mmoffitt 6/23/05 10:36:27 AM Reply	Re: just tables. Unless they are clustered. bcnu, Mikem It would seem, therefore, that the three human impulses embodied in religion are fear, conceit, and hatred. The purpose of religion, one might say, is to give an air of respectibility to these passions. -- Bertrand Russell

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