Deitel - Python, How To Program.pdf

pythonhtp1_17.fm Page 590 Wednesday, December 19, 2001 2:46 PM
590 Database Application Programming Interface (DB-API) Chapter 17
Title ISBN
First-
Name
Last-
Name
Copyright
C# How To Program 0130622214 Harvey Deitel 2002 Prentice Hall
C++ How to Program 0130895717 Paul Deitel 2001 Prentice Hall
C++ How to Program 0130895717 Harvey Deitel 2001 Prentice Hall
C++ How to Program 0131173340 Paul Deitel 1994 Prentice Hall
C++ How to Program 0131173340 Harvey Deitel 1994 Prentice Hall
C++ How to Program 0135289106 Harvey Deitel 1998 Prentice Hall
C++ How to Program 0135289106 Paul Deitel 1998 Prentice Hall
e-Business and e-Commerce 0130323640
for Managers
Harvey Deitel 2000 Prentice Hall
e-Business and e-Commerce 0130323640 Kate Stein- 2000 Prentice Hall
for Managers
buhler
e-Business and e-Commerce 0130323640
for Managers
Paul Deitel 2000 Prentice Hall
e-Business and e-Commerce 013028419X
How to Program
Harvey Deitel 2001 Prentice Hall
e-Business and e-Commerce 013028419X
How to Program
Paul Deitel 2001 Prentice Hall
e-Business and e-Commerce 013028419X
How to Program
Tem Nieto 2001 Prentice Hall
We added indentation to the query in Fig. 17.22 to make the query more readable. Let
us now break down the query into its various parts. Lines 1–3 contain a comma-separated
list of the fields that the query returns; the order of the fields from left to right specifies the
fields’ order in the returned table. This query selects fields Title and ISBN from table
Titles, fields FirstName and LastName from table Authors, field Copyright
from table Titles and field PublisherName from table Publishers. For purposes
of clarity, we fully qualified each field name with its table name (e.g., Titles.ISBN).
Lines 5–10 specify the INNER JOIN operations used to combine information from the
various tables. There are three INNER JOIN operations. It is important to note that,
although an INNER JOIN is performed on two tables, either of those two tables can be the
result of another query or another INNER JOIN. We use parentheses to nest the INNER
JOIN operations; SQL evaluates the innermost set of parentheses first and then moves outward.
We begin with the INNER JOIN:
( Publishers INNER JOIN Titles
ON Publishers.PublisherID = Titles.PublisherID )
Publisher-
Name
Fig. Fig. 17.23 17.23 Portion of the result set produced by the query in Fig. 17.22. (Part 2 of 2.)
which joins the Publishers table and the Titles table ON the condition that the PublisherID
numbers in each table match. The resulting temporary table contains information
about each book and its publisher.