为了提高查询速度,合理的创建索引,类如
SELECT a.goods_name,a.goods_number,a.goods_price,a.goods_track,b.payment,b.confirm_time,b.pay_status,b.id,b.sn,b.ware_house,b.total_amount,b.final_amount,b.cpns_amount,b.sale_amount,b.cost_amount,`goods_count`,`pay_status`,b.ship_status,b.createtime,b.payment,b.order_status,b.pay_time,b.shr_name,b.shr_phone,b.shr_province,b.shr_phone,b.shr_province,b.shr_city,b.shr_area,b.shr_address,b.remark,b.order_from,b.send_time,b.pay_sn,c.spec_info,c.cost_price,d.company,d.list,d.is_error,e.shop_sn as goods_sn FROM sh_order_goods a left join sh_order b on a.order_id=b.id left join sh_product c on a.product_id=c.id left join sh_send d on a.order_id=d.order_id left join sh_goods e on a.goods_id=e.id ORDER BY id DESC
这种数据查询虽然能实现功能,但是,倘若遇上几百万数据量的时候,会产生超时,严重可能导致服务崩掉。原理即是1000*1000*1000,慢可想而知了,尽量使用单表查数据,做加法。尤其电商最忌讳联合查询。 |