[Collab-qa-commits] r1456 - udd/sql

[Andreas Tille]

Author: tille
Date: 2009-05-08 20:23:13 +0000 (Fri, 08 May 2009)
New Revision: 1456

Added:
   udd/sql/array_accum.sql
Log:
Create comma aggregate function


Added: udd/sql/array_accum.sql
===================================================================
--- udd/sql/array_accum.sql	                        (rev 0)
+++ udd/sql/array_accum.sql	2009-05-08 20:23:13 UTC (rev 1456)
@@ -0,0 +1,29 @@
+/******************************************************************************
+ * Sometimes it is practical to aggregate a collumn to a comma separated list *
+ * This is described at:                                                      *
+ *                                                                            *
+ *  http://www.zigo.dhs.org/postgresql/#comma_aggregate                       *
+ *                                                                            *
+ ******************************************************************************/
+
+CREATE AGGREGATE array_accum (anyelement) (
+    sfunc = array_append,
+    stype = anyarray,
+    initcond = '{}'
+); 
+
+/*****************************************************************************
+ * this can be used like this:                                               *
+ *     array_to_string(array_accum(column),',')                              *
+ * Example:                                                                  *
+ *                                                                           *
+   SELECT av.version, array_to_string(array_accum(architecture),',') FROM
+     ( SELECT architecture AS architecture, version FROM packages
+          WHERE package = 'gcc' GROUP BY architecture, version ORDER BY architecture
+     ) AS av
+     GROUP BY version ORDER BY version DESC;
+ *                                                                           *
+ *****************************************************************************/
+
+
+