Database bookCatalogs completed

Author: jorzel

arcade/databases/bookCatalogs.mysql

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+
+/*
+You have your very own library at home, and it's getting bigger and bigger with each passing month. You've decided to create a database in which to store information about your books, in the hope that it will help you remember which books you have in your library.
+
+Information about the books in your library is stored in the table catalogs, which contains the following columns:
+
+doc_id - the unique ID of the catalog;
+xml_doc - the catalog as an XML file in the following format:
+<catalog>
+  <book id="...">
+    <author>...</author>
+    <title>...</title>
+  </book>
+  <book id="...">
+    <author>...</author>
+    <title>...</title>
+  </book>
+  ...
+</catalog>.
+Each catalog represents the work of one distinct <author> in your library. There is exactly one <catalog> element in each xml_doc, and the id for each book is unique.
+
+Given the catalogs table, you want to find out which authors you have represented in your library. Your task is to create a new table with the author column that will contain all the distinct authors, sorted by their names.
+
+Example
+
+For given table catalogs
+
+doc_id	xml_doc
+1
+<catalog>
+ <book id="11">
+  <author>Chuck Palahniuk</author>
+  <title>Fight Club</title>
+ </book>
+ <book id="12">
+  <author>Chuck Palahniuk</author>
+  <title>Survivor</title>
+ </book>
+</catalog>
+2
+<catalog>
+ <book id="21">
+  <author>Bernard Werber</author>
+  <title>Les Thanatonautes</title>
+ </book>
+</catalog>
+3
+<catalog>
+ <book id="31">
+  <author>Boris Vian</author>
+  <title>The Big Sleep</title>
+ </book>
+ <book id="32">
+  <author>Boris Vian</author>
+  <title>The Lady in the Lake</title>
+ </book>
+ <book id="33">
+  <author>Boris Vian</author>
+  <title>The World of Null-A</title>
+ </book>
+</catalog>
+the output should be
+
+author
+Bernard Werber
+Boris Vian
+Chuck Palahniuk
+*/
+
+CREATE PROCEDURE booksCatalogs()
+BEGIN
+	select ExtractValue(xml_doc, '//book[1]/author') as author from catalogs order by author;
+END