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https://github.com/khibino/haskell-relational-record.git
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44 lines
1.1 KiB
Haskell
44 lines
1.1 KiB
Haskell
{-# LANGUAGE TemplateHaskell, MultiParamTypeClasses, FlexibleInstances #-}
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import Data.Int
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import Database.Relational.Query
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import Database.Relational.Query.TH
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$(defineTable defaultConfig
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"PUBLIC" "my_table"
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[ ("person", [t| String |])
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, ("family", [t| String |])
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, ("age" , [t| Int32 |])
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]
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[] [0] (Just 0))
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agesOfFamilies :: Relation () (String, Maybe Int32)
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agesOfFamilies = aggregateRelation $ do
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my <- query myTable
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gFam <- groupBy $ my ! family' -- Specify grouping key
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return $ gFam >< sum' (my ! age') -- Aggregated results
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agesOfFamiliesO :: Relation () (String, Maybe Int32)
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agesOfFamiliesO = aggregateRelation $ do
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my <- query myTable
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gFam <- groupBy $ my ! family'
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let s = sum' (my ! age')
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orderBy s Desc -- Only aggregated value is allowed to pass
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orderBy gFam Asc
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return $ gFam >< s
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ageRankOfFamilies :: Relation () ((Int64, String), Int32)
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ageRankOfFamilies = relation $ do
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my <- query myTable
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return $
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rank `over` do
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partitionBy $ my ! family' -- Monad to build window
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orderBy (my ! age') Desc
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><
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my ! family'
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><
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my ! age'
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