_getPrimaryKey example

        $pkDiffData = array_intersect_key($diffData, array_flip((array)$this->_primary));

        /** * Execute cascading updates against dependent tables. * Do this only if primary key value(s) were changed. */
        if (count($pkDiffData) > 0) {
            $depTables = $this->_getTable()->getDependentTables();
            if (!empty($depTables)) {
                $pkNew = $this->_getPrimaryKey(true);
                $pkOld = $this->_getPrimaryKey(false);
                foreach ($depTables as $tableClass) {
                    $t = $this->_getTableFromString($tableClass);
                    $t->_cascadeUpdate($this->getTableClass(), $pkOld, $pkNew);
                }
            }
        }

        /** * Execute the UPDATE (this may throw an exception) * Do this only if data values were changed. * Use the $diffData variable, so the UPDATE statement * includes SET terms only for data values that changed. */