1. Alternative databases CMSC 461 Michael Wilson

2. The power of relational databases  It’s often useful to have relational database power in unusual situations  Useful to organize data in a relational way  Quick to query  How do we do this?

3. Local DBMS?  Running a server locally would be far too costly for the use cases where such things would be useful  These are meant for much more serious applications  There are some much more straightforward libraries and tools we can use

4. SQLite  SQLite is one of the more common file- based databases  Fully featured DBMS  Can query, create tables, create indexes, create triggers  Primary keys, autoincrement

5. SQLite memory footprint  All features enabled, ~500 KB memory space  Can be reduced to as small as 4 KB given the right configuration  Speed vs. memory footprint

6. SQLite and your favorite applications  Firefox  Cookies.sqlite  Content-prefs.sqlite  Downloads.sqlite  Chrome

7. SQLite and mobile devices  Android  Built in!  There’s some Java froofiness in front of it, but it works well!  iOS  Depending on what you need: basically uses the SQLite C library  This library is not exactly easy to use

8. Downsides to SQLite databases?  Really more meant for C and C-like environments  C, C++, Objective C  Built into Android for some reason  We may want to have similar functionality in a JVM language (Java, Groovy, Jython, Clojure, etc.)

9. Java DBMSes  H2 is a Java DBMS  H2 is capable of making in-memory or disk- backed tables  Overall roughly the same concepts  Another Java DBMS  Very feature rich

10. H2, HSQLDB, and Hibernate  H2/HSQLDB are both compatible with Hibernate  Hibernate comes built in with H2 and HSQLDB “dialects”  Can still use the same hibernate calls  This allows you to use H2/HSQLDB as sort of a “prototyping” solution before you connect to a more production ready database

11. XML  XML is a very convenient storage mechanism  Can define arbitrary schemas  Can define data types  Can store a good amount of data in an XML document  With a sufficiently large enough data set, querying could be useful

12. XPath  Query language  NOT based on SQL  Querying based on nodes present in an XML document

13. Simple XML document Storm of Swords George R. R. Martin A Deepness in the Sky Vernor Vinge

14. Simple XPath query  /books/book/title  Will return all titles  /books/book/author  Will return all authors  /books//author  Returns all authors that are descendants under the “books” element  //title  Select all titles

15. More XML queriess  /books/book[2]  Select the second book in the list  /books/book[1]  Select the first book in the list  /books/book[@genre='fantasy']  Select all books where genre attribute = fantasy

16. XPath functions  count(//books)  Counts the number of books  concat(//book[@genre='fantasy']/title, ', ', //book[@genre='sci-fi']/title)  Outputs: Storm of Swords, A Deepness in the Sky

17. XPath applications  You can apply XPath to any XML file, which makes it really handy for extracting the data

18. XPath online tester  http://www.freeformatter.com/xpath- tester.html http://www.freeformatter.com/xpath- tester.html  Can test XPath query expressions here