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1. queryMaybe :: (MonadQualify ConfigureQuery m, MonadQuery m) => Relation () r -> m (Record Flat (Maybe r))

   relational-schemas	Database.Custom.SQLite3

   Join sub-query. Query result is Maybe. The combinations of query and queryMaybe express inner joins, left outer joins, right outer joins, and full outer joins. Here is an example of a right outer join:

   outerJoin = relation $ do
   e <- queryMaybe employee
   d <- query department
   on $ e ?! E.deptId' .=. just (d ! D.deptId')
   return $ (,) |$| e |*| d
   

2. queryMaybe' :: MonadQuery m => Relation p r -> m (PlaceHolders p, Record Flat (Maybe r))

   relational-schemas	Database.Custom.SQLite3

   Join sub-query with place-holder parameter p. Query result is Maybe.

3. showNumMaybe :: (SqlContext c, Num a, IsString b) => Record c (Maybe a) -> Record c (Maybe b)

   relational-schemas	Database.Custom.SQLite3

   Unsafely show number into string-like type in records.

4. sumMaybe :: (Num a, AggregatedContext ac, SqlContext ac) => Record Flat (Maybe a) -> Record ac (Maybe a)

   relational-schemas	Database.Custom.SQLite3

   Aggregation function SUM.

5. uniqueQueryMaybe' :: UniqueRelation p c r -> QueryUnique (PlaceHolders p, Record c (Maybe r))

   relational-schemas	Database.Custom.SQLite3

   Join unique sub-query with place-holder parameter p. Query result is Maybe.

6. catMaybes :: [Maybe a] -> [a]

   strict-base-types	Data.Maybe.Strict

   Analogous to catMaybes in Data.Maybe.

7. fromMaybe :: a -> Maybe a -> a

   strict-base-types	Data.Maybe.Strict

   Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.

8. listToMaybe :: [a] -> Maybe a

   strict-base-types	Data.Maybe.Strict

   Analogous to listToMaybe in Data.Maybe.

9. mapMaybe :: (a -> Maybe b) -> [a] -> [b]

   strict-base-types	Data.Maybe.Strict

   Analogous to mapMaybe in Data.Maybe.

10. hoistMaybe :: forall (m :: Type -> Type) x a . Monad m => x -> Maybe a -> EitherT x m a

    transformers-either	Control.Monad.Trans.Either

    Hoist Maybe a into Right a.

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