select case巧用 oracle

在做报表的时候，经常会用到分段统计数据，这时候，case就比较有用了：

小例子：

SELECT   sh.dc_code, g.bg_code,
                   TO_CHAR (ship_date, 'MM') AS ship_date,
                   SUM
                      (CASE
                          WHEN 2 >= NVL (p.pdt_packingweight, 0)
                             THEN pl.picked_qty
                          ELSE 0
                       END
                      ) AS weight1,
                   SUM
                      (CASE
                          WHEN NVL (p.pdt_packingweight, 0) > 2
                          AND 4 >= NVL (p.pdt_packingweight, 0)
                             THEN pl.picked_qty
                          ELSE 0
                       END
                      ) AS weight2

from  ......

where ........

group by  sh.dc_code, g.bg_code