This bit of code allows to put Haskell expressions inside SQL queries.

{-# LANGUAGE QuasiQuotes #-}
import Data.Time.Clock (getCurrentTime)
import Database.PostgreSQL.Simple
import Database.PostgreSQL.Simple.SqlQQ.Alt (sql)

testQuery c = do
  let dbName = "test_db"
  now <- getCurrentTime
  uncurry (query c)
    [sql|
      select * from pg_stat_activity
      where query_start < $(addUTCTime (-60) now)$
        and datname = $(dbName)$
    |]

Don't forget to enable OverloadedStrings extension, owherwise you can encounter errors like:

Couldn't match expected type ‘Query’ with actual type ‘[Char]’

== TODO

• SQL lexer