Merge 'rt_bug_41083' into 'trunk'

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / Manual / Cookbook.pod

diff --git a/lib/DBIx/Class/Manual/Cookbook.pod b/lib/DBIx/Class/Manual/Cookbook.pod
index b7fc30a..f4a5a45 100644 (file)
--- a/lib/DBIx/Class/Manual/Cookbook.pod
+++ b/lib/DBIx/Class/Manual/Cookbook.pod
@@ -303,7 +303,7 @@ You can write subqueries relatively easily in DBIC.
     name => [ 'Billy Joel', 'Brittany Spears' ],
   });
 
-  my $rs = $schema->resulset('CD')->search({
+  my $rs = $schema->resultset('CD')->search({
     artist_id => { 'IN' => $inside_rs->get_column('id')->as_query },
   });
 
@@ -312,10 +312,38 @@ The usual operators ( =, !=, IN, NOT IN, etc) are supported.
 B<NOTE>: You have to explicitly use '=' when doing an equality comparison.
 The following will B<not> work:
 
-  my $rs = $schema->resulset('CD')->search({
+  my $rs = $schema->resultset('CD')->search({
     artist_id => $inside_rs->get_column('id')->as_query,
   });
 
+=head3 Correlated subqueries
+
+  my $cdrs = $schema->resultset('CD');
+  my $rs = $cdrs->search({
+    year => {
+      '=' => $cdrs->search(
+        { artistid => { '=' => \'me.artistid' } },
+        { alias => 'inner' }
+      )->get_column('year')->max_rs->as_query,
+    },
+  });
+
+That creates the following SQL:
+
+  SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track
+    FROM cd me
+   WHERE year = (
+      SELECT MAX(inner.year)
+        FROM cd inner
+       WHERE artistid = me.artistid
+      )
+
+=head2 Where subqueries will work
+
+Currently, subqueries will B<only> work in the where-clause of a search. In
+other words, in the first hashref of a search() method. Work is being done
+to make them work as part of the second hashref (from, select, +select, etc).
+
 =head2 Predefined searches
 
 You can write your own L<DBIx::Class::ResultSet> class by inheriting from it