Fuzzy.cz

And now let's check some problems with the SQL queries and indexes. There are two basic problems related to indexes - using an index when the index should not be used (false positive) and not using an index when it should be used (false negative). If you don't know what indexes are or if you're not sure how they work, read something about it - for example my article basic principles of database indexes describes basics of indexes.

Are you using relational databases but the indexes are closed book for you? You absolutely don't know what the indexes are and how they work, or you are confused by various types of indexes (B-Tree, Hash, Bitmap) and you're not sure about their advantages or disadvantages? Or you just can't find out why a particular index is not used when evaluating a query? Maybe this article will help you to answer these questions ...