diff --git a/etiquette/photodb.py b/etiquette/photodb.py
index 0f11b61..d02ba17 100644
--- a/etiquette/photodb.py
+++ b/etiquette/photodb.py
@@ -630,15 +630,15 @@ class PDBPhotoMixin:
         searchhelpers.minmax('duration', duration, minimums, maximums, warning_bag=warning_bag)
 
         orderby = searchhelpers.normalize_orderby(orderby)
-        notnulls = []
+        notnulls = set()
         if extension or mimetype:
-            notnulls.append('extension')
+            notnulls.add('extension')
         if width or height or ratio or area:
-            notnulls.append('width')
+            notnulls.add('width')
         if bytes:
-            notnulls.append('bytes')
+            notnulls.add('bytes')
         if duration:
-            notnulls.append('duration')
+            notnulls.add('duration')
 
         if orderby is None:
             giveback_orderby = None
diff --git a/etiquette/searchhelpers.py b/etiquette/searchhelpers.py
index 5495680..b23d8fe 100644
--- a/etiquette/searchhelpers.py
+++ b/etiquette/searchhelpers.py
@@ -20,7 +20,7 @@ def build_query(orderby, notnulls, minimums, maximums, mmf_results=None):
 
     for (column, direction) in orderby:
         if column != 'RANDOM()':
-            notnulls.append(column)
+            notnulls.add(column)
 
     for column in notnulls:
         wheres.append(column + ' IS NOT NULL')