relational.hs

-- relational.hs

import Database.HDBC
import Database.HDBC.PostgreSQL
import Data.List

printTuples conn rel = quickQuery' conn ("SELECT DISTINCT * FROM " ++ rel) []
(⋈) = intercalate " NATURAL JOIN "
(π) fields rel1 = "(SELECT " ++ (intercalate "," fields) ++ " FROM " ++ rel1 ++ ") a"

-- no gchi

:m Database.HDBC Database.HDBC.PostgreSQL
:l relational.hs
let teste = π ["empno", "ename", "dname"] $ (⋈)  ["emp", "dept"]
conn <- connectPostgreSQL "host=localhost dbname=hdbtest user=hdbtest"
printTuples conn teste