Mercurial > urweb
diff demo/prose @ 410:c5a3d223f157
Sql demo
author | Adam Chlipala <adamc@hcoop.net> |
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date | Tue, 21 Oct 2008 18:44:52 -0400 |
parents | 81d9f42bb641 |
children | 6a0e54400805 |
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--- a/demo/prose Tue Oct 21 17:49:14 2008 -0400 +++ b/demo/prose Tue Oct 21 18:44:52 2008 -0400 @@ -59,3 +59,15 @@ <p>The <tt>ListFun</tt> module defines a functor for building list editing sub-applications. An argument to the functor <tt>Make</tt> must give the type to be stored in the lists, along with marshaling and unmarshaling functions. In return, the functor returns an entry point function.</p> <p>The <tt>ListShop</tt> modules ties everything together by instantiating <tt>ListFun.Make</tt> with structures for integers and strings. <tt>show</tt> and <tt>read</tt> can be used for marshaling and unmarshaling in both cases because they are type-class-generic.</p> + +sql.urp + +<p>We see a simple example of accessing a SQL database. The project file specifies the database to connect to.</p> + +<p>A <tt>table</tt> declaration declares a SQL table with rows of a particular record type. We can use embedded SQL syntax in a way that leads to all of our queries and updates being type-checked. Indeed, Ur/Web makes strong guarantees that it is impossible to execute invalid SQL queries or make bad assumptions about the types of tables for marshaling and unmarshaling (which happen implicitly).</p> + +<p>The <tt>list</tt> function implements an HTML table view of all rows in the SQL table. The <tt>queryX</tt> function takes two arguments: a SQL query and a function for generating XML fragments from query result rows. The query is run, and the fragments for the rows are concatenated together.</p> + +<p>Other functions demonstrate use of the <tt>dml</tt> function, for building a transaction from a SQL DML command. It is easy to insert antiquoted Ur code into queries and DML commands, and the type-checker catches mistakes in the types of the expressions that we insert.</p> + +<p>