SELECT pricelistid ,bednettypeid ,0 AS line_diameter ,0 AS varvalue FROM ( SELECT u_pricelist.pricelistid ,CASE @varclass WHEN 0 THEN 0 ELSE u_bednet_type.bednettypeid END AS bednettypeid FROM u_pricelist CROSS JOIN u_bednet_type ) v_varmx GROUP BY pricelistid ,bednettypeid 序 床网类别 价格表 线径MM 变量值