Problem about postgresql-simple

[Magicloud Magiclouds]

Hi,
  Anyone used this library? Just trying to use it and got problem.

  alias here is a String.
kerb.hs:18:9:
    No instance for (Database.PostgreSQL.Simple.Param.Param Char)
      arising from a use of `query'
    Possible fix:
      add an instance declaration for
      (Database.PostgreSQL.Simple.Param.Param Char)
    In a stmt of a 'do' block:
      rs <- query conn "select 0 from users where alias = ?" (alias)

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