How to use 'read' in haskell

Test.hs

processDbRequest :: Connection -> [String] -> String
processDbRequest conn record@(tableId:requestType:_:rawParams) =
  let params = extractParams rawParams
      tableId = read tableId
      recordId = read (params M.! 1)
  in case tableId of
         1 -> "yes"
         _ -> "oh no"

test.hs:7:10:
No instance for (Num String)
arising from the literal `1'
Possible fix: add an instance declaration for (Num String)
In the pattern: 1
In a case alternative: 1 -> "yes"
In the expression:
case tableId of {
1 -> "yes"
_ -> "oh no" }