diff --git a/test/src/Main.idr b/test/src/Main.idr
index 33581f4..802dd28 100644
--- a/test/src/Main.idr
+++ b/test/src/Main.idr
@@ -34,6 +34,7 @@ app = withDB ":memory:" $ do
     , IF_NOT_EXISTS createFiles
     , IF_NOT_EXISTS createUnits
     , IF_NOT_EXISTS createEmployees
+    , IF_NOT_EXISTS createEdges
     , insertMol $ M "Ethanol"    (Just "64-17-5") (Just 46.069) Compound
     , insertMol $ M "Strychnine" (Just "57-24-9") (Just 334.419) Compound
     , insertMol $ M "Atropine"   (Just "51-55-8") (Just 289.375) Compound
@@ -55,6 +56,14 @@ app = withDB ":memory:" $ do
     , insertEmployee $ E "Gundi" 2050.0 1
     , insertEmployee $ E "Valeri" 5010.0 1
     , insertEmployee $ E "Ronja" 4010.0 1
+    , insertEdge "A" "B"
+    , insertEdge "B" "C"
+    , insertEdge "B" "D"
+    , insertEdge "C" "E"
+    , insertEdge "C" "F"
+    , insertEdge "D" "F"
+    , insertEdge "F" "G"
+    , insertEdge "B" "F"
     ] ++ fromList (insertFile . file <$> [0..255])
 
   queryTable (mol TRUE) 1000 >>= printTable
@@ -78,5 +87,7 @@ app = withDB ":memory:" $ do
   queryTable unitStats 1000 >>= printTable
   putStrLn ""
 
+  queryTable parents 1000 >>= printTable
+
 main : IO ()
 main = runApp handlers app
diff --git a/test/src/Schema.idr b/test/src/Schema.idr
index d0572bb..9316425 100644
--- a/test/src/Schema.idr
+++ b/test/src/Schema.idr
@@ -48,6 +48,14 @@ Files =
     , C "content" BLOB
     ]
 
+public export
+Edges : SQLTable
+Edges =
+  table "edges"
+    [ C "u" TEXT
+    , C "v" TEXT
+    ]
+
 export
 createMolecules : Cmd TCreate
 createMolecules =
@@ -92,6 +100,15 @@ createEmployees =
     , UNIQUE ["name"]
     ]
 
+export
+createEdges : Cmd TCreate
+createEdges =
+  CREATE_TABLE Edges
+    [ PRIMARY_KEY ["u", "v"]
+    , NOT_NULL "u"
+    , NOT_NULL "v"
+    ]
+
 --------------------------------------------------------------------------------
 -- Idris Types
 --------------------------------------------------------------------------------
@@ -157,6 +174,10 @@ export
 insertFile : File -> Cmd TInsert
 insertFile = insert Files ["content"]
 
+export
+insertEdge : String -> String -> Cmd TInsert
+insertEdge u v = INSERT Edges ["u", "v"] [val u, val v]
+
 --------------------------------------------------------------------------------
 -- Query
 --------------------------------------------------------------------------------
@@ -232,3 +253,10 @@ tuples =
     ]
     `WHERE` ("m1.molweight" < "m2.molweight")
     `OFFSET` 2
+
+public export
+parents : LQuery [String]
+parents =
+  SELECT_DISTINCT
+    ["u"]
+    [< FROM $ Edges `AS` "e"]