Inside Microsoft® SQL Server® 2008: T-SQL Querying

Conclusion

This chapter was an introduction to the relational model. Basic terms such as type, tuple, relation, and attribute were explained. The meaning of a relation should be now clear to you, and you should recognize that you can treat a relation like a business entity or understand it like a predicate with propositions. You can also use this dual approach when manipulating relations; you can be prescriptive, by using relational algebra, or descriptive, by using relational calculus. The importance of data integrity and the means to maintain data integrity were emphasized. Namely, constraints were explained comprehensively. The problem of NULLs was discussed. The chapter concluded with a set of formal rules and principles for achieving a good ...