Fundamental difference between Primary/Clustered and Secondary/Non-Clustered index

clustered-indexindexnonclustered-index

Are

  1. Primary Index and Clustered Index similar in concept

  2. Secondary Index and Non-Clustered Index similar in concept

Best Answer

And it looks like curiosity didn't actually kill the cat :-). So I found this book Database System Concepts (Sixth Edition) online and it's freely available to be read. I've scratched it a bit and it turns out that it has the needed definition inside:

Primary index: in a sequentially ordered file, the index whose search key specifies the sequential order of the file. Also called clustering index. The search key of a primary index is usually but not necessarily the primary key.

Secondary index: an index whose search key specifies an order different from the sequential order of the file. Also called non-clustering index.

So there you have it. Now I suppose you were reading another book (by same author(s)) which was with tests inside (Q&A) and not this one with theory. I'd say you should use them both at the same time.

Now, I'm not sure that a general book would be the best way to start. Personally I'd start with any freely available kit (SQL Server Express, MySQL Lamp, Oracle XE, SQLite...whatever sounds good for your ear) and play with concepts and also their physical implementation. I'd say going also with examples will work better than just pure theory.

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