/usr/share/doc/libghc-postgresql-simple-doc/html/Database-PostgreSQL-Simple-SqlQQ.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Database.PostgreSQL.Simple.SqlQQ</title><link href="ocean.css" rel="stylesheet" type="text/css" title="Ocean" /><script src="haddock-util.js" type="text/javascript"></script><script type="text/javascript">//<![CDATA[
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</script></head><body><div id="package-header"><ul class="links" id="page-menu"><li><a href="src/Database-PostgreSQL-Simple-SqlQQ.html">Source</a></li><li><a href="index.html">Contents</a></li><li><a href="doc-index.html">Index</a></li></ul><p class="caption">postgresql-simple-0.4.0.2: Mid-Level PostgreSQL client library</p></div><div id="content"><div id="module-header"><table class="info"><tr><th>Stability</th><td>experimental</td></tr><tr><th>Maintainer</th><td>Leon P Smith &lt;leon@melding-monads.com&gt;</td></tr><tr><th>Safe Haskell</th><td>None</td></tr></table><p class="caption">Database.PostgreSQL.Simple.SqlQQ</p></div><div id="description"><p class="caption">Description</p><div class="doc empty">&nbsp;</div></div><div id="synopsis"><p id="control.syn" class="caption expander" onclick="toggleSection('syn')">Synopsis</p><ul id="section.syn" class="hide" onclick="toggleSection('syn')"><li class="src short"><a href="#v:sql">sql</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/template-haskell-2.8.0.0/Language-Haskell-TH-Quote.html#t:QuasiQuoter">QuasiQuoter</a></li></ul></div><div id="interface"><h1>Documentation</h1><div class="top"><p class="src"><a name="v:sql" class="def">sql</a> :: <a href="/usr/share/doc/ghc-doc/html/libraries/template-haskell-2.8.0.0/Language-Haskell-TH-Quote.html#t:QuasiQuoter">QuasiQuoter</a><a href="src/Database-PostgreSQL-Simple-SqlQQ.html#sql" class="link">Source</a></p><div class="doc"><p><code><a href="Database-PostgreSQL-Simple-SqlQQ.html#v:sql">sql</a></code> is a quasiquoter that eases the syntactic burden
 of writing big sql statements in Haskell source code.  For example:
</p><pre> {-# LANGUAGE QuasiQuotes #-}

 query conn [sql| SELECT column_a, column_b
                    FROM table1 NATURAL JOIN table2
                   WHERE ? &lt;= time AND time &lt; ?
                     AND name LIKE ?
                   ORDER BY size DESC
                   LIMIT 100                        |]
            (beginTime,endTime,string)
</pre><p>This quasiquoter attempts to mimimize whitespace;  otherwise the
 above query would consist of approximately half whitespace when sent
 to the database backend.  It also recognizes and strips out standard
 sql comments <a href="--.html">--</a>.
</p><p>The implementation of the whitespace reducer is currently incomplete.
 Thus it can mess up your syntax in cases where whitespace should be
 preserved as-is.  It does preserve whitespace inside standard SQL string
 literals.  But it can get confused by the non-standard PostgreSQL string
 literal syntax (which is the default setting in PostgreSQL 8 and below),
 the extended escape string syntax,  quoted identifiers,  and other similar
 constructs.
</p><p>Of course, this caveat only applies to text written inside the SQL
 quasiquoter; whitespace reduction is a compile-time computation and
 thus will not touch the <code>string</code> parameter above,  which is a run-time
 value.
</p><p>Also note that this will not work if the substring <code>|]</code> is contained
 in the query.
</p></div></div></div></div><div id="footer"><p>Produced by <a href="http://www.haskell.org/haddock/">Haddock</a> version 2.13.2</p></div></body></html>
libghc-postgresql-simple-doc 0.4.0.2-1 / usr / share / doc / libghc-postgresql-simple-doc / html / Database-PostgreSQL-Simple-SqlQQ.html
