diff --git a/Database/Groundhog.hs b/Database/Groundhog.hs
--- a/Database/Groundhog.hs
+++ b/Database/Groundhog.hs
@@ -1,50 +1,14 @@
 -- | This module exports the most commonly used functions and datatypes.
 --
--- The example below shows the most of the main features. See more examples in the examples directory.
---
--- @
---{-\# LANGUAGE GADTs, TypeFamilies, TemplateHaskell, QuasiQuotes, FlexibleInstances \#-}
---import Control.Monad.IO.Class (liftIO)
---import Database.Groundhog.TH
---import Database.Groundhog.Sqlite
---
---data Customer a = Customer {customerName :: String, remark :: a} deriving Show
---data Product = Product {productName :: String, quantity :: Int, customer :: Customer String} deriving Show
---
---'mkPersist' ('defaultCodegenConfig' {migrationFunction = Just \"migrateAll\"}) [groundhog|
--- - entity: Customer
---   constructors:
---     - name: Customer
---       uniques:
---         - name: NameConstraint
---           fields: [customerName]
--- - entity: Product
--- |]
---
---main = withSqliteConn \":memory:\" $ runDbConn $ do
---  -- Customer is also migrated because Product references it.
---  -- It is possible to migrate schema for given type, e.g. migrate (undefined :: Customer String), or run migrateAll
---  'runMigration' 'defaultMigrationLogger' migrateAll
---  let john = Customer \"John Doe\" \"Phone: 01234567\"
---  johnKey <- 'insert' john
---  -- John is inserted only once because of the name constraint
---  insert $ Product \"Apples\" 5 john
---  insert $ Product \"Melon\" 2 john
---  -- Groundhog prevents SQL injections. Quotes and other special symbols are safe.
---  insert $ Product \"Melon\" 6 (Customer \"Jack Smith\" \"Don't let him pay by check\")
---  -- Bonus melon for all large melon orders. The values used in expressions should have known type, so literal 5 is annotated.
---  'update' [QuantityField '=.' toArith QuantityField + 1] (ProductNameField '==.' \"Melon\" '&&.' QuantityField '>.' (5 :: Int))
---  productsForJohn <- 'select' $ CustomerField ==. johnKey
---  liftIO $ putStrLn $ \"Products for John: \" ++ show productsForJohn
---  -- Check bonus
---  melon <- select $ (ProductNameField ==. \"Melon\") \`orderBy\` ['Desc' QuantityField]
---  liftIO $ putStrLn $ \"Melon orders: \" ++ show melon
--- @
+-- See the @examples@ directory in the package archive or <http://github.com/lykahb/groundhog/tree/master/examples>.
+
 module Database.Groundhog (
   -- * Main definitions
     PersistBackend(..)
   , DbPersist(..)
   , Key
+  , DefaultKey
+  , AutoKey
   , Unique
   , BackendSpecific
   , extractUnique
diff --git a/Database/Groundhog/Core.hs b/Database/Groundhog/Core.hs
--- a/Database/Groundhog/Core.hs
+++ b/Database/Groundhog/Core.hs
@@ -116,12 +116,12 @@
 data Unique (u :: (* -> *) -> *)
 -- | Key marked with this type can have value for any backend
 data BackendSpecific
--- | A phantom datatype to make instance head diffirent @c (ConstructorMarker, v)@
+-- | A phantom datatype to make instance head diffirent @c (ConstructorMarker v)@
 data ConstructorMarker v a
--- | A phantom datatype to make instance head diffirent @u (UniqueMarker, v)@
+-- | A phantom datatype to make instance head diffirent @u (UniqueMarker v)@
 data UniqueMarker v a
 
--- | A holder for DB type in backend-specific keys
+-- | It allows to store autogenerated keys of one database in another
 data KeyForBackend db v = (DbDescriptor db, PersistEntity v) => KeyForBackend (AutoKeyType db)
 
 data Proxy a
@@ -265,7 +265,7 @@
   insertByAll   :: PersistEntity v => v -> m (Either (AutoKey v) (AutoKey v))
   -- | Replace a record with the given autogenerated key. Result is undefined if the record does not exist.
   replace       :: (PersistEntity v, PrimitivePersistField (Key v BackendSpecific)) => Key v BackendSpecific -> v -> m ()
-  -- | Return a list of the records satisfying the condition. Example: @select $ (FirstField ==. \"abc\" &&. SecondField >. \"def\") \`orderBy\` [Asc ThirdField] \`limitBy\` 100@
+  -- | Return a list of the records satisfying the condition. Example: @select $ (FirstField ==. \"abc\" &&. SecondField >. \"def\") \`orderBy\` [Asc ThirdField] \`limitTo\` 100@
   select        :: (PersistEntity v, Constructor c, HasSelectOptions opts (PhantomDb m) (RestrictionHolder v c))
                 => opts -> m [v]
   -- | Return a list of all records. Order is undefined. It is useful for datatypes with multiple constructors.
@@ -285,10 +285,10 @@
   -- | Count total number of records with all constructors
   countAll      :: PersistEntity v => v -> m Int
   -- | Fetch projection of some fields. Example: @project (SecondField, ThirdField) $ (FirstField ==. \"abc\" &&. SecondField >. \"def\") \`orderBy\` [Asc ThirdField] \`offsetBy\` 100@
-  project       :: (PersistEntity v, Constructor c, Projection p (PhantomDb m) (RestrictionHolder v c) a', HasSelectOptions opts (PhantomDb m) (RestrictionHolder v c))
+  project       :: (PersistEntity v, Constructor c, Projection p (PhantomDb m) (RestrictionHolder v c) a, HasSelectOptions opts (PhantomDb m) (RestrictionHolder v c))
                 => p
                 -> opts
-                -> m [a']
+                -> m [a]
   -- | Check database schema and create migrations for the entity and the entities it contains
   migrate       :: PersistEntity v => v -> Migration m
   -- | Execute raw query
@@ -483,8 +483,8 @@
   toPurePersistValues :: DbDescriptor db => Proxy db -> a -> ([PersistValue] -> [PersistValue])
   fromPurePersistValues :: DbDescriptor db => Proxy db -> [PersistValue] -> (a, [PersistValue])
 
--- | Datatypes which can be converted directly to 'PersistValue'. The no-value parameter @DbDescriptor db => Proxy db@ allows conversion depend the database details while keeping it pure.
-class (SinglePersistField a, PurePersistField a) => PrimitivePersistField a where
+-- | Datatypes which can be converted directly to 'PersistValue'. The no-value parameter @DbDescriptor db => Proxy db@ allows conversion depend the database details while keeping it pure. A type which has an instance of 'PrimitivePersistField' should be an instance of superclasses 'SinglePersistField' and 'PurePersistField' as well.
+class PersistField a => PrimitivePersistField a where
   toPrimitivePersistValue :: DbDescriptor db => Proxy db -> a -> PersistValue
   fromPrimitivePersistValue :: DbDescriptor db => Proxy db -> PersistValue -> a
 
diff --git a/Database/Groundhog/Expression.hs b/Database/Groundhog/Expression.hs
--- a/Database/Groundhog/Expression.hs
+++ b/Database/Groundhog/Expression.hs
@@ -42,10 +42,11 @@
 instance (PersistEntity v, Constructor c, PersistField a, RestrictionHolder v c ~ r') => Expression db r' (SubField v c a) where
   toExpr = ExprField . fieldChain
 
-instance (PersistEntity v, Constructor c, PersistField (Key v BackendSpecific), FieldLike (AutoKeyField v c) db r' a') => Expression db r' (AutoKeyField v c) where
+instance (PersistEntity v, Constructor c, RestrictionHolder v c ~ r') => Expression db r' (AutoKeyField v c) where
   toExpr = ExprField . fieldChain
 
-instance (PersistEntity v, FieldLike (u (UniqueMarker v)) db r' a', r' ~ RestrictionHolder v (UniqueConstr (Key v (Unique u))),  IsUniqueKey (Key v (Unique u))) => Expression db r' (u (UniqueMarker v)) where
+instance (PersistEntity v, IsUniqueKey k, k ~ Key v (Unique u), RestrictionHolder v (UniqueConstr k) ~ r')
+      => Expression db r' (u (UniqueMarker v)) where
   toExpr = ExprField . fieldChain
 
 -- Let's call "plain type" the types that uniquely define type of a Field it is compared to.
diff --git a/Database/Groundhog/Generic.hs b/Database/Groundhog/Generic.hs
--- a/Database/Groundhog/Generic.hs
+++ b/Database/Groundhog/Generic.hs
@@ -21,6 +21,10 @@
   -- * Helper functions for defining *PersistValue instances
   , primToPersistValue
   , primFromPersistValue
+  , primToPurePersistValues
+  , primFromPurePersistValues
+  , primToSinglePersistValue
+  , primFromSinglePersistValue
   , pureToPersistValue
   , pureFromPersistValue
   , singleToPersistValue
@@ -58,7 +62,6 @@
 import Data.Either (partitionEithers)
 import Data.Function (on)
 import Data.List (partition, sortBy)
-import Data.Maybe (fromMaybe)
 import qualified Data.Map as Map
 
 getCorrectMigrations :: NamedMigrations -> [(Bool, Int, String)]
@@ -164,20 +167,20 @@
   DbEmbedded emb -> DbEmbedded $ applyToDef emb
   DbEntity (Just (emb, uniq)) onDel onUpd e -> DbEntity (Just (applyToDef emb, uniq)) onDel onUpd e
   t -> error $ "applyEmbeddedDbTypeSettings: expected DbEmbedded, got " ++ show t) where
-  applyToDef (EmbeddedDef _ fields) = EmbeddedDef True $ go settings fields
-  go [] fs = fs
+  applyToDef (EmbeddedDef _ fields) = uncurry EmbeddedDef $ go settings fields
+  go [] fs = (False, fs)
   go st [] = error $ "applyEmbeddedDbTypeSettings: embedded datatype does not have following fields: " ++ show st
-  go st (f@(fName, fType):fs) = case find fName st of
-    Just (rest, PSEmbeddedFieldDef _ dbName dbTypeName subs) -> (fromMaybe fName dbName, typ'):go rest fs where
+  go st (f@(fName, fType):fs) = case partition ((== fName) . psEmbeddedFieldName) st of
+    ([PSEmbeddedFieldDef _ dbName dbTypeName subs], rest) -> result where
+      (flag, fields') = go rest fs
+      result = case dbName of
+        Nothing -> (flag, (fName, typ'):fields')
+        Just name' -> (True, (name', typ'):fields')
       typ' = case (subs, dbTypeName) of
         (Just e, _) -> applyEmbeddedDbTypeSettings e fType
         (_, Just typeName) -> DbOther (OtherTypeDef $ const typeName)
         _ -> fType
-    Nothing -> f:go st fs
-  find :: String -> [PSEmbeddedFieldDef] -> Maybe ([PSEmbeddedFieldDef], PSEmbeddedFieldDef)
-  find _ [] = Nothing
-  find name (def:defs) | psEmbeddedFieldName def == name = Just (defs, def)
-                       | otherwise = fmap (\(defs', result) -> (def:defs', result)) $ find name defs
+    _ -> let (flag, fields') = go st fs in (flag, f:fields')
 
 applyReferencesSettings :: Maybe ReferenceActionType -> Maybe ReferenceActionType -> DbType -> DbType
 applyReferencesSettings onDel onUpd typ = case typ of
@@ -192,6 +195,19 @@
 primFromPersistValue (x:xs) = phantomDb >>= \p -> return (fromPrimitivePersistValue p x, xs)
 primFromPersistValue xs = (\a -> fail (failMessage a xs) >> return (a, xs)) undefined
 
+primToPurePersistValues :: (DbDescriptor db, PrimitivePersistField a) => Proxy db -> a -> ([PersistValue] -> [PersistValue])
+primToPurePersistValues p a = (toPrimitivePersistValue p a:)
+
+primFromPurePersistValues :: (DbDescriptor db, PrimitivePersistField a) => Proxy db -> [PersistValue] -> (a, [PersistValue])
+primFromPurePersistValues p (x:xs) = (fromPrimitivePersistValue p x, xs)
+primFromPurePersistValues _ xs = (\a -> error (failMessage a xs) `asTypeOf` (a, xs)) undefined
+
+primToSinglePersistValue :: (PersistBackend m, PrimitivePersistField a) => a -> m PersistValue
+primToSinglePersistValue a = phantomDb >>= \p -> return (toPrimitivePersistValue p a)
+
+primFromSinglePersistValue :: (PersistBackend m, PrimitivePersistField a) => PersistValue -> m a
+primFromSinglePersistValue a = phantomDb >>= \p -> return (fromPrimitivePersistValue p a)
+
 pureToPersistValue :: (PersistBackend m, PurePersistField a) => a -> m ([PersistValue] -> [PersistValue])
 pureToPersistValue a = phantomDb >>= \p -> return (toPurePersistValues p a)
 
@@ -207,7 +223,7 @@
 
 toSinglePersistValueUnique :: forall m v u . (PersistBackend m, PersistEntity v, IsUniqueKey (Key v (Unique u)), PrimitivePersistField (Key v (Unique u)))
                            => u (UniqueMarker v) -> v -> m PersistValue
-toSinglePersistValueUnique u v = insertBy u v >> toSinglePersistValue (extractUnique v :: Key v (Unique u))
+toSinglePersistValueUnique u v = insertBy u v >> primToSinglePersistValue (extractUnique v :: Key v (Unique u))
 
 fromSinglePersistValueUnique :: forall m v u . (PersistBackend m, PersistEntity v, IsUniqueKey (Key v (Unique u)), PrimitivePersistField (Key v (Unique u)))
                              => u (UniqueMarker v) -> PersistValue -> m v
@@ -223,7 +239,7 @@
 
 toSinglePersistValueAutoKey :: forall m v . (PersistBackend m, PersistEntity v, PrimitivePersistField (AutoKey v))
                             => v -> m PersistValue
-toSinglePersistValueAutoKey a = insertByAll a >>= toSinglePersistValue . either id id
+toSinglePersistValueAutoKey a = insertByAll a >>= primToSinglePersistValue . either id id
 
 fromSinglePersistValueAutoKey :: forall m v . (PersistBackend m, PersistEntity v, PrimitivePersistField (Key v BackendSpecific))
                               => PersistValue -> m v
diff --git a/Database/Groundhog/Instances.hs b/Database/Groundhog/Instances.hs
--- a/Database/Groundhog/Instances.hs
+++ b/Database/Groundhog/Instances.hs
@@ -2,10 +2,8 @@
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 module Database.Groundhog.Instances (Selector(..)) where
 
-import Control.Monad (liftM)
-
 import Database.Groundhog.Core
-import Database.Groundhog.Generic (failMessage, primToPersistValue, primFromPersistValue, pureFromPersistValue, phantomDb)
+import Database.Groundhog.Generic (primToPersistValue, primFromPersistValue, primToPurePersistValues, primFromPurePersistValues, primToSinglePersistValue, primFromSinglePersistValue, pureFromPersistValue, phantomDb)
 
 import qualified Data.Text as T
 import qualified Data.Text.Encoding as T
@@ -56,28 +54,7 @@
   selectorNum Tuple5_2Selector = 2
   selectorNum Tuple5_3Selector = 3
   selectorNum Tuple5_4Selector = 4
-  
-instance PrimitivePersistField a => SinglePersistField a where
-  toSinglePersistValue a = phantomDb >>= \p -> return (toPrimitivePersistValue p a)
-  fromSinglePersistValue a = phantomDb >>= \p -> return (fromPrimitivePersistValue p a)
 
-instance (SinglePersistField a, NeverNull a) => SinglePersistField (Maybe a) where
-  toSinglePersistValue Nothing = return PersistNull
-  toSinglePersistValue (Just a) = toSinglePersistValue a
-  fromSinglePersistValue PersistNull = return Nothing
-  fromSinglePersistValue a = liftM Just $ fromSinglePersistValue a
-
-instance PrimitivePersistField a => PurePersistField a where
-  toPurePersistValues p a = (toPrimitivePersistValue p a:)
-  fromPurePersistValues p (x:xs) = (fromPrimitivePersistValue p x, xs)
-  fromPurePersistValues _ xs = (\a -> error (failMessage a xs) `asTypeOf` (a, xs)) undefined
-
-instance (PrimitivePersistField a, NeverNull a) => PurePersistField (Maybe a) where
-  toPurePersistValues p a = (maybe PersistNull (toPrimitivePersistValue p) a:)
-  fromPurePersistValues _ (PersistNull:xs) = (Nothing, xs)
-  fromPurePersistValues p (x:xs) = (fromPrimitivePersistValue p x, xs)
-  fromPurePersistValues _ xs = (\a -> error (failMessage a xs) `asTypeOf` (a, xs)) undefined
-
 instance PurePersistField () where
   toPurePersistValues _ _ = id
   fromPurePersistValues _ xs = ((), xs)
@@ -226,6 +203,166 @@
   toPrimitivePersistValue p (KeyForBackend a) = toPrimitivePersistValue p a
   fromPrimitivePersistValue p x = KeyForBackend (fromPrimitivePersistValue p x)
 
+instance SinglePersistField String where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField T.Text where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField ByteString where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Int where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Int8 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Int16 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Int32 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Int64 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Word8 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Word16 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Word32 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Word64 where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Double where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Bool where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField Day where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField TimeOfDay where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField UTCTime where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance SinglePersistField ZonedTime where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance (PrimitivePersistField a, NeverNull a) => SinglePersistField (Maybe a) where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance (DbDescriptor db, PersistEntity v) => SinglePersistField (KeyForBackend db v) where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance PurePersistField String where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField T.Text where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField ByteString where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Int where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Int8 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Int16 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Int32 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Int64 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Word8 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Word16 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Word32 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Word64 where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Double where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Bool where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField Day where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField TimeOfDay where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField UTCTime where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance PurePersistField ZonedTime where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance (PrimitivePersistField a, NeverNull a) => PurePersistField (Maybe a) where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
+instance (DbDescriptor db, PersistEntity v) => PurePersistField (KeyForBackend db v) where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
 instance NeverNull String
 instance NeverNull T.Text
 instance NeverNull ByteString
@@ -460,7 +597,7 @@
   projectionExprs e = (ExprRaw e:)
   projectionResult _ = fromPersistValues
 
-instance (PersistEntity v, Constructor c, PersistField (Key v BackendSpecific)) => Projection (AutoKeyField v c) db (RestrictionHolder v c) (Key v BackendSpecific) where
+instance (PersistEntity v, Constructor c, a ~ AutoKey v) => Projection (AutoKeyField v c) db (RestrictionHolder v c) a where
   projectionExprs f = (ExprField (fieldChain f):)
   projectionResult _ = fromPersistValues
 
@@ -471,8 +608,8 @@
     constr = constructors e !! phantomConstrNum c
   projectionResult c xs = toSinglePersistValue (phantomConstrNum c) >>= \cNum -> fromEntityPersistValues (cNum:xs)
 
-instance (PersistEntity v, IsUniqueKey (Key v (Unique u)), r ~ RestrictionHolder v (UniqueConstr (Key v (Unique u))))
-      => Projection (u (UniqueMarker v)) db r (Key v (Unique u)) where
+instance (PersistEntity v, IsUniqueKey k, k ~ Key v (Unique u), r ~ RestrictionHolder v (UniqueConstr k))
+      => Projection (u (UniqueMarker v)) db r k where
   projectionExprs u = ((map ExprField chains)++) where
     UniqueDef _ _ uFields = constrUniques constr !! uniqueNum ((undefined :: u (UniqueMarker v) -> Key v (Unique u)) u)
     chains = map (\f -> (f, [])) uFields
@@ -514,27 +651,27 @@
     return ((a, b, c, d, e), rest4)
 
 instance (PersistEntity v, Constructor c, Projection (AutoKeyField v c) db r a') => Assignable (AutoKeyField v c) db r a'
-
 instance (PersistEntity v, Constructor c, Projection (SubField v c a) db r a') => Assignable (SubField v c a) db r a'
-
 instance (PersistEntity v, Constructor c, Projection (Field v c a) db r a') => Assignable (Field v c a) db r a'
-
 instance (PersistEntity v, IsUniqueKey (Key v (Unique u)), Projection (u (UniqueMarker v)) db r a') => Assignable (u (UniqueMarker v)) db r a'
 
-instance (PersistEntity v, Constructor c, Projection (AutoKeyField v c) db r a') => FieldLike (AutoKeyField v c) db r a' where
+instance (PersistEntity v, Constructor c, a ~ AutoKey v) => FieldLike (AutoKeyField v c) db (RestrictionHolder v c) a where
   fieldChain a = chain where
-    chain = maybe (error "fieldChain AutoKeyField: constructor constrAutoKeyName == Nothing") (\idName -> ((idName, DbEntity Nothing Nothing Nothing e), [])) $ constrAutoKeyName constr
+    chain = ((name, dbType k), [])
+    -- if it is Nothing, the name would not be used because the type will be () with no columns
+    name = maybe "will_be_ignored" id $ constrAutoKeyName $ constructors e !! cNum
+    k = (undefined :: AutoKeyField v c -> AutoKey v) a
     e = entityDef ((undefined :: AutoKeyField v c -> v) a)
     cNum = phantomConstrNum ((undefined :: AutoKeyField v c -> c (ConstructorMarker v)) a)
-    constr = constructors e !! cNum
 
-instance (PersistEntity v, Constructor c, Projection (SubField v c a) db r a') => FieldLike (SubField v c a) db r a' where
+instance (PersistEntity v, Constructor c, PersistField a) => FieldLike (SubField v c a) db (RestrictionHolder v c) a where
   fieldChain (SubField a) = a
 
-instance (PersistEntity v, Constructor c, Projection (Field v c a) db r a') => FieldLike (Field v c a) db r a' where
+instance (PersistEntity v, Constructor c, PersistField a) => FieldLike (Field v c a) db (RestrictionHolder v c) a where
   fieldChain = entityFieldChain
 
-instance (PersistEntity v, IsUniqueKey (Key v (Unique u)), Projection (u (UniqueMarker v)) db r a') => FieldLike (u (UniqueMarker v)) db r a' where
+instance (PersistEntity v, IsUniqueKey k, k ~ Key v (Unique u), r ~ RestrictionHolder v (UniqueConstr k))
+      => FieldLike (u (UniqueMarker v)) db r k where
   fieldChain u = chain where
     UniqueDef _ _ uFields = constrUniques constr !! uniqueNum ((undefined :: u (UniqueMarker v) -> Key v (Unique u)) u)
     chain = (("will_be_ignored", DbEmbedded $ EmbeddedDef True $ uFields), [])
diff --git a/examples/basic.hs b/examples/basic.hs
--- a/examples/basic.hs
+++ b/examples/basic.hs
@@ -1,38 +1,36 @@
-{-# LANGUAGE GADTs, TypeFamilies, TemplateHaskell, QuasiQuotes, FlexibleInstances #-}
+{-# LANGUAGE GADTs, TypeFamilies, TemplateHaskell, QuasiQuotes, FlexibleInstances, StandaloneDeriving #-}
 import Control.Monad.IO.Class (liftIO)
 import Database.Groundhog.TH
 import Database.Groundhog.Sqlite
 
-data Customer a = Customer {customerName :: String, remark :: a} deriving Show
-data Product = Product {productName :: String, quantity :: Int, customer :: Customer String} deriving Show
+data Customer = Customer {customerName :: String, phone :: String} deriving Show
+data Product = Product {productName :: String, quantity :: Int, customer :: DefaultKey Customer}
+deriving instance Show Product
 
--- Code generator will derive the necessary instances and generate other boilerplate code for the entities defined below.
--- It will also create function migrateAll that migrates schema for all non-polymorphic entities 
-mkPersist (defaultCodegenConfig {migrationFunction = Just "migrateAll"}) [groundhog|
-- entity: Customer
+mkPersist defaultCodegenConfig [groundhog|
+- entity: Customer               # Name of the datatype
   constructors:
     - name: Customer
+      fields:
+        - name: customerName
+          dbName: name           # Set column name to "name" instead of "customerName"
       uniques:
         - name: NameConstraint
-          fields: [customerName]
+          fields: [customerName] # Inline format of list
 - entity: Product
 |]
 
-main = withSqliteConn ":memory:" $ runDbConn $ do
-  -- Customer is also migrated because Product references it.
-  -- It is possible to migrate schema for given type, e.g. migrate (undefined :: Customer String), or run migrateAll
-  runMigration defaultMigrationLogger migrateAll
-  let john = Customer "John Doe" "Phone: 01234567"
-  johnKey <- insert john
-  -- John is inserted only once because of the name constraint
-  insert $ Product "Apples" 5 john
-  insert $ Product "Melon" 2 john
-  -- Groundhog prevents SQL injections. Quotes and other special symbols are safe.
-  insert $ Product "Melon" 6 (Customer "Jack Smith" "Don't let him pay by check")
+main = withSqliteConn "mydb.sqlite" $ runDbConn $ do
+  runMigration defaultMigrationLogger $ do
+    migrate (undefined :: Customer)
+    migrate (undefined :: Product)
+  johnKey <- insert $ Customer "John Doe" "0123456789"
+  get johnKey >>= liftIO . print
+  insert $ Product "Apples" 5 johnKey
+  insert $ Product "Melon" 3 johnKey
+  janeKey <- insert $ Customer "Jane Doe" "987654321"
+  insert $ Product "Oranges" 4 janeKey
   -- bonus melon for all large melon orders. The values used in expressions should have known type, so literal 5 is annotated.
   update [QuantityField =. toArith QuantityField + 1] (ProductNameField ==. "Melon" &&. QuantityField >. (5 :: Int))
-  productsForJohn <- select $ CustomerField ==. johnKey
+  productsForJohn <- select $ (CustomerField ==. johnKey) `orderBy` [Asc ProductNameField]
   liftIO $ putStrLn $ "Products for John: " ++ show productsForJohn
-  -- check bonus
-  melon <- select $ (ProductNameField ==. "Melon") `orderBy` [Desc QuantityField]
-  liftIO $ putStrLn $ "Melon orders: " ++ show melon
diff --git a/examples/dbSpecificTypes.hs b/examples/dbSpecificTypes.hs
--- a/examples/dbSpecificTypes.hs
+++ b/examples/dbSpecificTypes.hs
@@ -20,6 +20,15 @@
   fromPersistValues = primFromPersistValue
   dbType _ = DbOther $ OtherTypeDef $ const "point"
 
+-- These two instances of superclasses are useful but not necessary. They are like Functor and Applicative instances when you implement a Monad.
+instance SinglePersistField Point where
+  toSinglePersistValue = primToSinglePersistValue
+  fromSinglePersistValue = primFromSinglePersistValue
+
+instance PurePersistField Point where
+  toPurePersistValues = primToPurePersistValues
+  fromPurePersistValues = primFromPurePersistValues
+
 data MobilePhone = MobilePhone {number :: String, prepaidMoney :: String, location :: Point, ipAddress :: String} deriving Show
 
 mkPersist defaultCodegenConfig [groundhog|
diff --git a/examples/keys.hs b/examples/keys.hs
--- a/examples/keys.hs
+++ b/examples/keys.hs
@@ -4,15 +4,19 @@
 import Database.Groundhog.TH
 import Database.Groundhog.Sqlite
 
--- artistName is a unique key
 data Artist = Artist { artistName :: String } deriving (Eq, Show)
+data Album  = Album  { albumName :: String} deriving (Eq, Show)
+-- We cannot use regular deriving because when it works, the Key Eq and Show instances for (Key Album BackendSpecific) are not created yet
+data Track  = Track  { albumTrack :: Key Album BackendSpecific, trackName :: String }
+deriving instance Eq Track
+deriving instance Show Track
 
 mkPersist defaultCodegenConfig [groundhog|
 definitions:
   - entity: Artist
     autoKey:
       constrName: AutoKey
-      default: false # Defines if this key is used when an entity is stored directly, for example, data Ref = Ref SomeEntity
+      default: false # Defines if this key is used when an entity is stored directly, for example, data Ref = Ref Artist
     keys:
       - name: ArtistName
         default: true
@@ -23,20 +27,6 @@
             # Optional parameter type can be constraint (by default), index, or primary
             type: constraint
             fields: [artistName]
-|]
-
-data Album  = Album  { albumName :: String} deriving (Eq, Show)
--- many-to-many relation
-data ArtistAlbum = ArtistAlbum {artist :: Key Artist (Unique ArtistName), album :: Key Album BackendSpecific }
-deriving instance Eq ArtistAlbum
-deriving instance Show ArtistAlbum
--- We cannot use regular deriving because when it works, the Key Eq and Show instances for (Key Album BackendSpecific) are not created yet
-data Track  = Track  { albumTrack :: Key Album BackendSpecific, trackName :: String }
-deriving instance Eq Track
-deriving instance Show Track
-
-mkPersist defaultCodegenConfig [groundhog|
-definitions:
   - entity: Album
   - entity: Track
     constructors:
@@ -46,9 +36,17 @@
   # Configure actions on parent table changes
             onDelete: cascade
             onUpdate: restrict
-  # Keys of many-to-many relation form a unique key
+|]
+
+-- Many-to-many relation. It is defined here because ArtistName is available only after the the definitions for Artist are created
+data ArtistAlbum = ArtistAlbum {artist :: Key Artist (Unique ArtistName), album :: Key Album BackendSpecific }
+deriving instance Eq ArtistAlbum
+deriving instance Show ArtistAlbum
+
+mkPersist defaultCodegenConfig [groundhog|
+definitions:
   - entity: ArtistAlbum
-    autoKey: null
+    autoKey: null # Disable creation of the autoincrement integer key
     keys:
       - name: ArtistAlbumKey
         default: true
@@ -76,5 +74,4 @@
   [albumKey'] <- project AlbumField $ (ArtistField ==. ArtistNameKey "John Lennon") `limitTo` 1
   -- order by primary key
   tracks' <- select $ (AlbumTrackField ==. albumKey') `orderBy` [Desc AutoKeyField] `limitTo` 3
-  liftIO $ print tracks'
-
+  liftIO $ print tracks'
diff --git a/examples/rawQueries.hs b/examples/rawQueries.hs
--- a/examples/rawQueries.hs
+++ b/examples/rawQueries.hs
@@ -1,7 +1,7 @@
 {-# LANGUAGE GADTs, TypeFamilies, TemplateHaskell, QuasiQuotes, FlexibleInstances #-}
 import Control.Monad (liftM, (>=>))
 import Control.Monad.IO.Class (liftIO)
-import Database.Groundhog.Core (PersistValue, PersistField(..), PrimitivePersistField(..), RowPopper)
+import Database.Groundhog.Core (PersistValue, PersistField(..), PrimitivePersistField(..), RowPopper, PersistEntity(..))
 import Database.Groundhog.Generic (mapAllRows, phantomDb)
 import Database.Groundhog.TH
 import Database.Groundhog.Sqlite
diff --git a/examples/withoutQuasiQuotes.hs b/examples/withoutQuasiQuotes.hs
--- a/examples/withoutQuasiQuotes.hs
+++ b/examples/withoutQuasiQuotes.hs
@@ -9,8 +9,8 @@
 mkPersist defaultCodegenConfig $ PersistDefinitions [
   Left $ PSEntityDef "Table" Nothing Nothing Nothing Nothing $ Just [
     PSConstructorDef "Create" Nothing Nothing Nothing (Just [
-        PSFieldDef "select" (Just "SELECT") Nothing Nothing Nothing
-      , PSFieldDef "fubar" (Just "BEGIN COMMIT") Nothing Nothing Nothing
+        PSFieldDef "select" (Just "SELECT") Nothing Nothing Nothing Nothing Nothing
+      , PSFieldDef "fubar" (Just "BEGIN COMMIT") Nothing Nothing Nothing Nothing Nothing
       ])
       Nothing
     ]
diff --git a/groundhog.cabal b/groundhog.cabal
--- a/groundhog.cabal
+++ b/groundhog.cabal
@@ -1,5 +1,5 @@
 name:            groundhog
-version:         0.3.0.1
+version:         0.3.1
 license:         BSD3
 license-file:    LICENSE
 author:          Boris Lykah <lykahb@gmail.com>