php+mysql的联合查询的简单问题~ 例如： 我想从表m_ralation中查询name,ad... 想从m_address中查

SELECT m_ralation.name AS name, m_address.ad AS ad, m_address.postcode AS postcode FROM m_ralation, m_address WHERE m_ralation.ad=m_address.ad and m_ralation.ad='$sAddress'