# HG changeset patch
# User Nicolas Chauvat <nicolas.chauvat@logilab.fr>
# Date 1300181882 -3600
# Node ID 6beb7f1e05faa3285b5b8030fcb3058887d1a8e2
# Parent  a828feedc16446a594dfa9ac92cc092136973921
[doc] complete description of EXISTS in rql/language.rst

diff -r a828feedc164 -r 6beb7f1e05fa doc/book/en/annexes/rql/language.rst
--- a/doc/book/en/annexes/rql/language.rst	Tue Mar 15 09:41:45 2011 +0100
+++ b/doc/book/en/annexes/rql/language.rst	Tue Mar 15 10:38:02 2011 +0100
@@ -153,7 +153,7 @@
 - Aggregate Functions: COUNT, MIN, MAX, AVG, SUM, GROUP_CONCAT
 
 Having
-``````
+```````
 
 The HAVING clause, as in SQL, has been originally introduced to restrict a query
 according to value returned by an aggregate function, e.g.::
@@ -214,7 +214,12 @@
 
 
 Exists
-``````
+```````
+
+You can use `EXISTS` when you want to know if some expression is true and do not
+need the complete set of elements that make it true. Testing for existence is
+much faster than fetching the complete set of results.
+
 ::
 
     Any X ORDERBY PN,N