| Safe Haskell | None |
|---|---|
| Language | Haskell98 |
Opaleye.Aggregate
Description
Perform aggregations on query results.
- aggregate :: Aggregator a b -> Query a -> Query b
- groupBy :: Aggregator (Column a) (Column a)
- sum :: Aggregator (Column a) (Column a)
- count :: Aggregator (Column a) (Column PGInt8)
- avg :: Aggregator (Column PGFloat8) (Column PGFloat8)
- max :: PGOrd a => Aggregator (Column a) (Column a)
- min :: PGOrd a => Aggregator (Column a) (Column a)
- boolOr :: Aggregator (Column PGBool) (Column PGBool)
- boolAnd :: Aggregator (Column PGBool) (Column PGBool)
- arrayAgg :: Aggregator (Column a) (Column (PGArray a))
- stringAgg :: Column PGText -> Aggregator (Column PGText) (Column PGText)
- data Aggregator a b
Documentation
aggregate :: Aggregator a b -> Query a -> Query b Source
Given a Query producing rows of type a and an Aggregator accepting rows of
type a, apply the aggregator to the results of the query.
groupBy :: Aggregator (Column a) (Column a) Source
Group the aggregation by equality on the input to groupBy.
sum :: Aggregator (Column a) (Column a) Source
Sum all rows in a group.
data Aggregator a b Source
An Aggregator takes a collection of rows of type a, groups
them, and transforms each group into a single row of type b. This
corresponds to aggregators using GROUP BY in SQL.
An Aggregator corresponds closely to a Fold from the
foldl package. Whereas an Aggregator a b takes each group of
type a to a single row of type b, a Fold a b
takes a list of a and returns a single row of type b.