opaleye-0.4.2.0: An SQL-generating DSL targeting PostgreSQL

Safe HaskellNone
LanguageHaskell98

Opaleye.Order

Synopsis

Documentation

orderBy :: Order a -> Query a -> Query a Source

Order the rows of a Query according to the Order.

import Data.Monoid (<>)

-- Order by the first column ascending.  When first columns are equal
-- order by second column descending.
example :: Query (Column PGInt4, Column PGText)
        -> Query (Column PGInt4, Column PGText)
example = orderBy (asc fst <> desc snd)

asc :: PGOrd b => (a -> Column b) -> Order a Source

Specify an ascending ordering by the given expression. (Any NULLs appear last)

desc :: PGOrd b => (a -> Column b) -> Order a Source

Specify an descending ordering by the given expression. (Any NULLs appear first)

ascNullsFirst :: PGOrd b => (a -> Column b) -> Order a Source

Specify an ascending ordering by the given expression. (Any NULLs appear first)

descNullsLast :: PGOrd b => (a -> Column b) -> Order a Source

Specify an descending ordering by the given expression. (Any NULLs appear last)

limit :: Int -> Query a -> Query a Source

Limit the results of the given query to the given maximum number of items.

offset :: Int -> Query a -> Query a Source

Offset the results of the given query by the given amount, skipping that many result rows.

class PGOrd a Source

Typeclass for Postgres types which support ordering operations.

Instances

data Order a Source

An Order represents an expression to order on and a sort direction. Multiple Orders can be composed with mappend. If two rows are equal according to the first Order, the second is used, and so on.

Instances