public function getPrimaryKey($table)
    {
        $this->checkTableArgument($table);
        $pks = $this->getPrimaryKeys($table);
        if (count($pks) > 1) {
            $keys = implode(',', $pks);
            throw new Exception\MultiplePrimaryKeyException(__METHOD__ . ". Multiple primary keys found on table '$table':  $keys");
        }
        return $pks[0];
    }
public function getPrimaryKey($table)
    {
        $this->checkTableArgument($table);
        $pks = $this->getPrimaryKeys($table);
        if (count($pks) > 1) {
            $keys = implode(',', $pks);
            throw new Exception\MultiplePrimaryKeyException(__METHOD__ . ". Multiple primary keys found on table '$table':  $keys");
        }
        return $pks[0];
    }
public function getPrimaryKey ( $ table ) { $ this -> checkTableArgument ( $ table ) ; $ pks = $ this -> getPrimaryKeys ( $ table ) ; if ( count ( $ pks ) > 1 ) { $ keys = implode ( ',' , $ pks ) ; throw new Exception \ MultiplePrimaryKeyException ( __METHOD__ . ". Multiple primary keys found on table '$table':  $keys" ) ; } return $ pks [ 0 ] ; }
Return unique table primary key

@throws Exception\InvalidArgumentException
@throws Exception\ErrorException
@throws Exception\NoPrimaryKeyException when no pk
@throws Exception\MultiplePrimaryKeyException when multiple pk found
@throws Exception\ExceptionInterface
@throws Exception\TableNotFoundException

@param string $table
@return string|int primary key
Return unique table primary key