<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>pbh</author><text>To answer a few of the database questions that keep popping up in this thread:&lt;p&gt;1.  Is it worth understanding relational algebra?  Yes.  Definitely.  It&apos;s not that hard, there&apos;s more or less a one-to-one mapping of relational algebra to SQL.  Relational algebra is both a useful mathematical tool and indispensable when trying to understand query optimization.  Relational algebra is also necessary to be able to read pretty much any of the database literature, if that&apos;s one of your goals.  (Just be thankful you don&apos;t have to learn Relational Calculus or Datalog.)&lt;p&gt;2.  Is it worth learning XML features like XML DTDs, XPath, XML Schema, and XQuery?  Yes, definitely.  I don&apos;t like XML, but there are tons of places where you can use XPath.  (The most interesting thing about XQuery is probably how similar it is to SQL, though.)&lt;p&gt;3.  Is it worth learning about SQL triggers?  Probably.  Ultimately, the web development world is split between people for whom separation of concerns means doing more in the database, and those for whom separation of concerns means doing less in the database.  If you think doing validation and transactions in the database is sensible, triggers are also a sensible thing to learn about.  However, people like DHH disagree and want validation in your app server with a dumber backend.&lt;p&gt;4.  Is this vocational training?  Well, this is the first in a three class sequence at Stanford.  This class is mostly about schema and query languages, so in some sense, it&apos;s the most useful to practitioners (or at least, non-DBA practitioners).  The second class is about systems and implementation (on-disk layout, indexing structures, query optimization).  In the third class, students either learn about distributed databases or actually build their own from scratch.  However, schema and query languages have enough theory behind them, and enough generality, that I wouldn&apos;t consider it any more vocational training than a class on compilers.</text><parent_chain></parent_chain></comment><story><title>Enrollment for Stanford&apos;s online DB class now open</title><url>http://www.db-class.org/course/auth/welcome</url><text></text></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>skymt</author><text>As are the AI and ML classes.&lt;p&gt;&lt;a href=&quot;http://www.ai-class.com/&quot; rel=&quot;nofollow&quot;&gt;http://www.ai-class.com/&lt;/a&gt;
&lt;a href=&quot;http://www.ml-class.org/&quot; rel=&quot;nofollow&quot;&gt;http://www.ml-class.org/&lt;/a&gt;</text><parent_chain></parent_chain></comment><story><title>Enrollment for Stanford&apos;s online DB class now open</title><url>http://www.db-class.org/course/auth/welcome</url><text></text></story>