SQL and Relational Theory: How to Write Accurate SQL Code - download pdf or read online

By C. J. Date

ISBN-10: 149194112X

ISBN-13: 9781491941126

SQL is stuffed with problems and traps for the unwary. you could keep away from them should you comprehend relational idea, yet provided that you know the way to place that concept into perform. during this booklet, Chris Date explains relational idea intensive, and demonstrates via a variety of examples and routines how one can use it on your use of SQL.

This 3rd version has been revised, prolonged, and more advantageous all through. subject matters whose therapy has been extended comprise facts varieties and domain names, desk comparisons, photograph relatives, mixture operators and summarization, view updating, and subqueries. a distinct characteristic of this version is a brand new appendix on NoSQL and relational theory.

* may you write an SQL question to discover staff who've labored once or more in each programming division within the corporation? And verify it’s correct?
* Why is right column naming so important?
* Nulls within the database reason mistaken solutions. Why? What you are able to do approximately it?
* How can picture kin assist you formulate advanced SQL queries?
* SQL helps "quantified comparisons," yet they’re greater shunned. Why? And how?

Database idea and perform have developed significantly seeing that Codd first outlined the relational version, again in 1969. This booklet attracts on a long time of expertise to give the hottest therapy of the fabric to be had anyplace. someone with a modest to complex heritage in SQL can enjoy the insights it includes. The e-book is product self reliant.

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Extra info for SQL and Relational Theory: How to Write Accurate SQL Code (3rd Edition)

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Here’s an SQL example: CREATE VIEW SST_PARIS AS ( SELECT SNO , STATUS FROM S WHERE CITY = 'Paris' ) ; In principle, you can operate on views just as if they were base relations,13 but they aren’t base relations. Instead, you can think of a view as being “materialized”—in effect, you can think of a base relation being constructed whose value is obtained by evaluating the specified relational expression—at the time the view in question is referenced. But I must emphasize that thinking of views as being materialized in this way when they’re referenced is purely conceptual; it’s just a way of thinking; it’s not what’s really supposed to happen; and it wouldn’t work for update operations in any case.

A tuple with three components (a tuple of degree three). n Every subset of a heading is a heading. For example, consider the heading of the suppliers relation in Fig. 3. That heading has four attributes: SNO, SNAME, STATUS, and CITY. And if we remove (say) the SNAME and STATUS attributes, what’s left is still a heading, a heading of degree two. n Every subset of a body is a body. For example, consider the body of the suppliers relation in Fig. 3. That body has five tuples, corresponding to the five suppliers S1, S2, S3, S4, 22 Chapter 1 / Setting the Scene and S5.

Product Returns a relation containing all possible tuples that are a combination of two tuples, one from each of two specified relations. Note: This operator is also known variously as cartesian product (sometimes more specifically extended or expanded cartesian product), cross product, cross join, and cartesian join; in fact, it’s really just a special case of join, as we’ll see in Chapter 6. 8 Except that Codd additionally defined an operator called divide. I’ll explain in Chapter 7 why I omit that operator here.

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SQL and Relational Theory: How to Write Accurate SQL Code (3rd Edition) by C. J. Date


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