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  1. mapMaybe :: forall s k a b . (a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

    refined-containers Data.Map.Strict.Refined

    Apply a function to all values in a map and collect only the Just results, returning a potentially smaller map.

  2. mapMaybeWithKey :: (Key s k -> a -> Maybe b) -> Map s k a -> SomeMapWith (SupersetProof 'Regular s) k b

    refined-containers Data.Map.Strict.Refined

    Apply a function to all values in a map, together with their corresponding keys, and collect only the Just results, returning a potentially smaller map.

  3. flattenMaybe :: ProjectableMaybe p => p (Maybe (Maybe a)) -> p (Maybe a)

    relational-record Database.Relational.Documentation

    Compose nested Maybe phantom type on record.

  4. fromMaybe :: (OperatorContext c, HasColumnConstraint NotNull r) => Record c r -> Record c (Maybe r) -> Record c r

    relational-record Database.Relational.Documentation

    Operator from maybe type using record extended isNull.

  5. negateMaybe :: (OperatorContext c, Num a) => Record c (Maybe a) -> Record c (Maybe a)

    relational-record Database.Relational.Documentation

    Number negate uni-operator corresponding SQL -.

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

    relational-record Database.Relational.Documentation

    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

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

    relational-record Database.Relational.Documentation

    Aggregation function SUM.

  8. class ProjectableFlattenMaybe a b

    relational-schemas Database.Custom.IBMDB2

    Interface to compose phantom Maybe nested type.

  9. class ProjectableMaybe (p :: Type -> Type)

    relational-schemas Database.Custom.IBMDB2

    Interface to control Maybe of phantom type in records.

  10. avgMaybe :: (Num a, Fractional b, AggregatedContext ac, SqlContext ac) => Record Flat (Maybe a) -> Record ac (Maybe b)

    relational-schemas Database.Custom.IBMDB2

    Aggregation function AVG.

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