#' PostgreSQL - Delete postgresql database table
#' @details PostgreSql andmebaasi tabeli kustutamine.
#' @param con An PostgreSQLConnection object as produced by dbConnect.
#' @param tbl The database table name.
#' @return eturn message.
#' @seealso \code{\link{myPostgresConnect}}, \code{\link{myPostgresDropTable}},
#' \code{\link{myPostgresCreateGisDb}}, \code{\link{myPostgresImprotShp}}
#' @examples \dontrun{
#' con <- myPostgresConnect(host = '192.168.255.26', port = 5432,
#'        user = 'osm', password = 'osm', dbname = 'shp')
#' myPostgresDropTable(con = con, tbl = "xxx")
#'
#' }
#'
#' @export
#'

myPostgresDropTable <- function(con = NULL, tbl) {
  # Check is connection valid
  if(is.null(con) || !DBI::dbIsValid(con)){
    message(paste0("DB connection is not valid!"))
    return()
  }
  # Check if db exists
  if(!DBI::dbExistsTable(con, tolower(tbl))){
    DBI::dbDisconnect(con)
    message(paste0("Tabel ", tbl, " doesn't exist."))
    return()
  }
  # Drop table
  q <- paste("drop table if exists ", tbl, ";")
  res <- DBI::dbSendQuery(con, q)
  DBI::dbHasCompleted(res)
  DBI::dbClearResult(res)
  DBI::dbDisconnect(con)
}