SQL多重级联查询讨论?
wxch 2009-05-21 10:45:10 订单表(dd)
字段:
流水号(dd_id),dd_htbianhao(合同编号),dd_kehu(客户),...
产品明细表(ddmx)
字段:
流水号(ddmx_id),ddmx_ddid(对应订单表流水号),ddmx_mingcheng(产品名称),...
工单表(gd)
字段:
流水号(gd_id),gd_ddmxid(对应产品明细表流水号),gd_ljmingcheng(零件名称),...
工时表(gdmx):
字段:
流水号:(gdmx_id),gdmx_gdid(对应工单表流水号),gdmx_jgzhanghao(加工人),gdmx_hegepin(加工合格品数量),...
如果要查询"张三"的gdmx_hegepin(加工合格品数量),有如下SQL语句:
select dd_htbianhao(合同编号),dd_kehu(客户),ddmx_mingcheng(产品名称),gd_ljmingcheng(零件名称), gdmx_hegepin(加工合格品) from dd,ddmx,gd,gdmx where dd_id=ddmx_id and ddmx_id=gd_ddmxid and gd_id=gdmx_gdid and gdmx_jgzhanghao like '张三'
请问如何改写上面的语句,才能使多重级联的查询效率更高?