diff --git a/reference/pgsql/functions/pg-affected-rows.xml b/reference/pgsql/functions/pg-affected-rows.xml
index dd0a8ed0ae..50605678c0 100644
--- a/reference/pgsql/functions/pg-affected-rows.xml
+++ b/reference/pgsql/functions/pg-affected-rows.xml
@@ -19,6 +19,10 @@
    <literal>UPDATE</literal>, and <literal>DELETE</literal>
    queries. 
   </para>
+  <para>
+   Since PostgreSQL 9.0 and above, the server returns the number of 
+   SELECTed rows. Older PostgreSQL return 0 for SELECT.
+  </para>
   <note>
    <para>
     This function used to be called <function>pg_cmdtuples</function>.