Schema tuning is the activity of organizing a set of table designs in order to improve overall query and update performance.
Table design entails deciding which tables to implement and which attributes to put in those tables. Other sections of this encyclopedia (design theory, normalization theory) discuss a mathematical model of table design to eliminate redundancy. Sometimes however redundancy can be good for performance, so database tuners must consider the possibility of a principled incorporation of redundancy.
Blog(blog_id, author_id, title, numreaders) and
If one frequently wants to associate blogs with the city of their authors, then this table design requires a join on author_id for each of these queries. A denormalized alternative is to add author_location to
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