回答：四张表用LEFT join操作后丢失了一部分，说明是至少其中一张表不完整。依次跑下面四个脚本，对应哪次有问题就是对应新LEFT JOIN进来的哪张表数据残缺（即，WHERE那句上面的那张表）。SELECT 订单.`订单ID` FROM 订单WHERE 订单.`订单ID` IN ( "10248", "10254" );GOSELECT 订单.`订单ID` FROM 订单LEFT JOIN 运货商 ON 订单.`运货商` = 运货商.`运货商ID`WHERE 订单.`订单ID` IN ( "10248", "10254" );GOSELECT 订单.`订单ID` FROM 订单LEFT JOIN 运货商 ON 订单.`运货商` = 运货商.`运货商ID`LEFT JOIN 订单明细 ON 订单.`订单ID` = 订单明细.`订单ID`WHERE 订单.`订单ID` IN ( "10248", "10254" );GOSELECT 订单.`订单ID` FROM 订单LEFT JOIN 运货商 ON 订单.`运货商` = 运货商.`运货商ID`LEFT JOIN 订单明细 ON 订单.`订单ID` = 订单明细.`订单ID`LEFT JOIN 产品 ON 订单明细.`产品ID` = 产品.`产品ID` WHERE 订单.`订单ID` IN ( "10248", "10254" );GO