select * from message,reply where message.Id=reply.MsId
查询两张表(message.Id=reply.MsId)的内容
两个表:
select message.*,reply.RpContent from message left join reply on message.Id = reply.MsId
查询message表全部内容 和 reply表(message.Id = reply.MsId)的内容
三个表:
SELECT subshop. * , coupon. * , color. *
FROM subshop
LEFT JOIN coupon ON subshop.Id = coupon.ShopId
LEFT JOIN color ON coupon.ColorId = color.ColorId