xquery return value off by one
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<title>Compilers</title>
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<author>Alfred V. Aho</author>
<author>Ravi Sethi</author>
<author>Jeffrey D. Ullman</author>
</authors>
<publisher>Addison Wesley</publisher>
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<title>Database Driven Web Sites</title>
<authors><author>Jesse Feiler</author></authors>
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<genre>Web sites</genre>
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</authors>
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<genre>Computers</genre>
<genre>Database Engineering</genre>
<genre>Database Management - General</genre>
<genre>Database management</genre>
</genres>
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<book asin="0130402648"
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<uuid>1C60074A-6CDF-11D9-830B-000393D3DE16</uuid>
<title>Database System Implementation</title>
<authors>
<author>Hector Garcia-Molina</author>
<author>Jeffrey D. Ullman</author>
<author>Jennifer D. Widom</author>
</authors>
<publisher>Prentice Hall</publisher>
<published>1999-06-11</published>
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<title>Database Systems: The Complete Book</title>
<authors>
<author>Hector Garcia-Molina</author>
<author>Jeffrey D. Ullman</author>
<author>Jennifer D. Widom</author>
</authors>
<publisher>Prentice Hall</publisher>
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<title>Computer Networking: A Top-Down Approach Featuring the Internet</title>
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<author>James F. Kurose</author>
<author>Keith W. Ross</author>
<author>James Kurose</author>
<author>Keith Ross</author>
</authors>
<publisher>Addison Wesley</publisher>
<published>2002-07-17</published>
<price>100.00</price>
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<title>Computer Networks and Internets, Fourth Edition</title>
<authors>
<author>Douglas E Comer</author>
<author>Ralph E. Droms</author>
</authors>
<publisher>Prentice Hall</publisher>
<published>2003-07-28</published>
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<title>Essentials of Programming Languages - 2nd Edition</title>
<authors>
<author>Daniel P. Friedman</author>
<author>Mitchell Wand</author>
<author>Christopher T. Haynes</author>
</authors>
<publisher>The MIT Press</publisher>
<published>2001-01-29</published>
<price>62.00</price>
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<title>Operating System Concepts</title>
<authors>
<author>Abraham Silberschatz</author>
<author>Greg Gagne</author>
<author>Peter Baer Galvin</author>
</authors>
<publisher>Wiley</publisher>
<published>2002-03-08</published>
<price>107.95</price>
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<uuid>1C764AD4-6CDF-11D9-830B-000393D3DE16</uuid>
<title>Artificial Intelligence: A Modern Approach (2nd Edition)</title>
<authors>
<author>Stuart J. Russell</author>
<author>Peter Norvig</author>
</authors>
<publisher>Prentice Hall</publisher>
<published>2002-12-20</published>
<price>93.33</price>
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<book asin="155860832X"
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<uuid>1C898640-6CDF-11D9-830B-000393D3DE16</uuid>
<title>Computer Networks: A Systems Approach, 3rd Edition</title>
<authors>
<author>Larry L. Peterson</author>
<author>Bruce S. Davie</author>
</authors>
<publisher>Morgan Kaufmann</publisher>
<published>2003-05-22</published>
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<title>SQL Fundamentals (2nd Edition)</title>
<authors><author>John J. Patrick</author></authors>
<publisher>Prentice Hall PTR</publisher>
<published>2002-05-07</published>
<price>54.99</price>
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<title>Fundamentals of Database Systems, Fourth Edition</title>
<authors>
<author>Ramez Elmasri</author>
<author>Shamkant B. Navathe</author>
</authors>
<publisher>Addison Wesley</publisher>
<published>2003-07-23</published>
<price>104.20</price>
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<uuid>F3C7B24F-6CDC-11D9-830B-000393D3DE16</uuid>
<title>A Complete Guide to DB2 Universal Database</title>
<authors>
<author>D. D. Chamberlin</author>
<author>Don Chamberlin</author>
</authors>
<publisher>Morgan Kaufmann</publisher>
<published>1998-08-15</published>
<edition>Paperback</edition>
<price>62.95</price>
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<genre>Computer Bks - Data Base Management</genre>
<genre>Computer Books: Database</genre>
<genre>Computers</genre>
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<genre>General</genre>
<genre>IBM Database 2</genre>
<genre>Information Storage & Retrieval</genre>
<genre>Relational Databases</genre>
<genre>Computers / Information Storage & Retrieval</genre>
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<title>DB2: The Complete Reference (Complete Reference Series)</title>
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<author>Roman B. Melnyk</author>
<author>Paul C. Zikopoulos</author>
</authors>
<publisher>McGraw-Hill Companies</publisher>
<published>2001-10-01</published>
<price>59.99</price>
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<uuid>F6B97E54-6CDC-11D9-830B-000393D3DE16</uuid>
<title>DB2 UDB v8 Handbook for Windows and UNIX/Linux</title>
<authors><author>Philip K. Gunning</author></authors>
<publisher>Prentice Hall PTR</publisher>
<published>2003-08-06</published>
<price>59.99</price>
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<title>DB2 SQL Procedural Language for Linux, Unix and Windows</title>
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<author>Paul Yip</author>
<author>Drew Bradstock</author>
<author>Hana Curtis</author>
<author>Michael Gao</author>
<author>Zamil Janmohamed</author>
<author>Clara Liu</author>
<author>Fraser McArthur</author>
</authors>
<publisher>Prentice Hall PTR</publisher>
<published>2002-12-24</published>
<price>59.99</price>
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<title>DB2 UDB V8.1 Certification Exam 700 Study Guide</title>
<authors><author>Roger E. Sanders</author></authors>
<publisher>Prentice Hall PTR</publisher>
<published>2003-09-17</published>
<price>49.99</price>
<purchaseDate>2005-01-22</purchaseDate>
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created="128136024"
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<title>DB2 Fundamentals Certification for Dummies</title>
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<author>Paul C. Zikopoulos</author>
<author>Jennifer Gibbs</author>
<author>Roman B. Melnyk</author>
</authors>
<publisher>For Dummies</publisher>
<published>2001-08-01</published>
<price>34.99</price>
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<uuid>F6D9A3D8-6CDC-11D9-830B-000393D3DE16</uuid>
<title>DB2 Universal Database V8 for Linux, UNIX, and Windows Database Administration Certification Guide (5th Edition)</title>
<authors>
<author>George Baklarz</author>
<author>Bill Wong</author>
</authors>
<publisher>Prentice Hall PTR</publisher>
<published>2003-02-10</published>
<price>59.99</price>
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<title>Advanced DBA Certification Guide and Reference for DB2 UDB v8 for Linux, Unix and Windows</title>
<authors>
<author>Dwaine R. Snow</author>
<author>Thomas Xuan Phan</author>
<author>Dwaine Snow</author>
</authors>
<publisher>Prentice Hall PTR</publisher>
<published>2003-07-07</published>
<price>59.99</price>
<purchaseDate>开发者_如何转开发;2005-01-22</purchaseDate>
</book>
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created="128136024"
lastLookupTime="128136024">
<uuid>F6E1063D-6CDC-11D9-830B-000393D3DE16</uuid>
<title>Advanced Database Systems (The Morgan Kaufmann Series in Data Management Systems)</title>
<authors>
<author>Carlo Zaniolo</author>
<author>Stefano Ceri</author>
<author>Christos Faloutsos</author>
<author>Richard T. Snodgrass</author>
<author>V. S. Subrahmanian</author>
<author>Roberto Zicari</author>
</authors>
<publisher>Morgan Kaufmann</publisher>
<published>1997-05-01</published>
<price>88.95</price>
<purchaseDate>2005-01-22</purchaseDate>
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<book asin="0131840487"
created="128136024"
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<uuid>F6E441CE-6CDC-11D9-830B-000393D3DE16</uuid>
<title>DB2 UDB V8.1 Certification Exams 701 and 706 Study Guide</title>
<authors><author>Roger E. Sanders</author></authors>
<publisher>Prentice Hall PTR</publisher>
<published>2003-12-12</published>
<price>49.99</price>
<purchaseDate>2005-01-22</purchaseDate>
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created="128136024"
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<uuid>F6E77C2C-6CDC-11D9-830B-000393D3DE16</uuid>
<title>DB2 High Performance Design and Tuning</title>
<authors>
<author>Richard Yevich</author>
<author>Susan Lawson</author>
<author>Richard A. Yevich</author>
</authors>
<publisher>Prentice Hall PTR</publisher>
<published>2000-08-24</published>
<price>54.99</price>
<purchaseDate>2005-01-22</purchaseDate>
</book>
</recommendations>
</book>
</items>
<borrowers>
<borrower id="1">
<name> John Doe </name>
<phone> 555-1212 </phone>
<borrowed>
<book asin="0138613370"/>
<book asin="0122513363"/>
</borrowed>
</borrower>
<borrower id="2">
<name> Mary Jane </name>
<phone> 555-1213 </phone>
<borrowed>
<book asin="0201100886"/>
<book asin="0122513363"/>
</borrowed>
</borrower>
<borrower id="3">
<name> Bill Jones </name>
<phone> 555-1312 </phone>
<borrowed />
</borrower>
<borrower id="4">
<name> Anne Marie</name>
<phone> 555-1314</phone>
<borrowed>
<book asin="0138613370"/>
<book asin="0201100886"/>
<book asin="0122513363"/>
<book asin="1558604820"/>
</borrowed>
</borrower>
</borrowers>
</library>
I need to return everyone that borrowed a book, their name and the title of the book.
Here is my xQuery:
xquery version "1.0";
for $library in doc("library.xml")/library
for $book in $library/items/book
let $borrowed := $library/borrowers/borrower
return
<borrower>
<name>
{data($borrowed/name)}
</name>
<title>
{data($book[@asin = $borrowed//book/@asin]/title)}
</title>
</borrower>
Here is what it returns:
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title>Compilers</title>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title>Database Driven Web Sites</title>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title/>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title/>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title/>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title>First Course in Database Systems, A</title>
</borrower>
<borrower>
<name> John Doe Mary Jane Bill Jones Anne Marie</name>
<title>A Complete Guide to DB2 Universal Database</title>
</borrower>
So first thing that is wrong is that it is returning all the names of people who have borrowed a book instead of one name per tag. Second, it should return 8 books and its only returning 7.
Can anyone please help me understand what is wrong with my xQuery????
I'm pretty sure you're trying to get a list of each borrower with the titles of the books they have borrowed. The problem with your XQuery is that you are iterating over each /library/items/book instead of each borrower. Also, there are only 7 /library/items/book in your example; not 8.
This XQuery should do what you want.
XQuery
<borrowers>
{
let $library := doc('library.xml')
for $borrower in $library/library/borrowers/borrower
let $name := $borrower/name
let $asins := data($borrower/borrowed/book/@asin)
let $titles :=
for $asin in $asins
return $library/library/items/book[@asin = $asin]/title
return
<borrower>
{$name}
{$titles}
</borrower>
}
</borrowers>
Results
<borrowers>
<borrower>
<name> John Doe </name>
<title>First Course in Database Systems, A</title>
<title>Database Driven Web Sites</title>
</borrower>
<borrower>
<name> Mary Jane </name>
<title>Compilers</title>
<title>Database Driven Web Sites</title>
</borrower>
<borrower>
<name> Bill Jones </name>
</borrower>
<borrower>
<name> Anne Marie</name>
<title>First Course in Database Systems, A</title>
<title>Compilers</title>
<title>Database Driven Web Sites</title>
<title>A Complete Guide to DB2 Universal Database</title>
</borrower>
</borrowers>
I have no experience with XQuery, but as far as I can see, your predicate [@asin = $borrowed//book/@asin] should be moved into the let statement, otherwise there is no connection, no link between $book and $borrowed at all. And since you already have a specific book in $book, there is no need for the predicate when returning the book title.
Frankly, I would probably take another approach: instead of looping over the books, why don't you loop over the borrowers? After all, you "need to return everyone that borrowed a book, their name and the title of the book"…
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