oracle nvl()函數在使用中出現的問題

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看一條sql

select q.*, r.goods_name
  from (select nvl(t.goods_code, s.goods_code) goods_code,
               t.buy_open_price,
               t.buy_position_price,
               t.buy_position_amount,
               s.sale_open_price,
               s.sale_position_price,
               s.sale_position_amount,
               (nvl(t.buy_position_amount, 0) -
               nvl(s.sale_position_amount, 0)) position_amount
          from (select opo.goods_code,
                       opo.position_bs,
                       sum(opo.open_price * opo.position_amount) /
                       sum(opo.position_amount) buy_open_price,
                       sum(opo.position_price * opo.position_amount) /
                       sum(opo.position_amount) buy_position_price,
                       sum(opo.position_amount) buy_position_amount
                  from otc_trade_position_open opo
                 where opo.position_bs = '1'
                   and opo.account_type = '1'
                   and position_bs = '2'
                 group by opo.goods_code, opo.position_bs) t
          full outer join (select opo.goods_code,
                                 opo.position_bs,
                                 sum(opo.open_price * opo.position_amount) /
                                 sum(opo.position_amount) sale_open_price,
                                 sum(opo.position_price *
                                     opo.position_amount) /
                                 sum(opo.position_amount) sale_position_price,
                                 sum(opo.position_amount) sale_position_amount
                            from otc_trade_position_open opo
                           where opo.position_bs = '2'
                             and opo.account_type = '1'
                             and position_bs = '2'
                           group by opo.goods_code, opo.position_bs) s
            on (t.goods_code = s.goods_code)) q
  left outer join otc_goods r
    on (q.goods_code = r.goods_code)

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結果以下

 

 

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再看下一個sql

select q.*, r.goods_name
  from (select nvl(t.goods_code, s.goods_code) goods_code,
               t.buy_open_price,
               t.buy_position_price,
               t.buy_position_amount,
               s.sale_open_price,
               s.sale_position_price,
               s.sale_position_amount,
               (nvl(t.buy_position_amount, 0) -
               nvl(s.sale_position_amount, 0)) position_amount
          from (select opo.goods_code,
                       opo.position_bs,
                       sum(opo.open_price * opo.position_amount) /
                       sum(opo.position_amount) buy_open_price,
                       sum(opo.position_price * opo.position_amount) /
                       sum(opo.position_amount) buy_position_price,
                       sum(opo.position_amount) buy_position_amount
                  from otc_trade_position_open opo
                 where opo.position_bs = '1'
                   and opo.account_type = '1'
                   and position_bs = '1'
                 group by opo.goods_code, opo.position_bs) t
          full outer join (select opo.goods_code,
                                 opo.position_bs,
                                 sum(opo.open_price * opo.position_amount) /
                                 sum(opo.position_amount) sale_open_price,
                                 sum(opo.position_price *
                                     opo.position_amount) /
                                 sum(opo.position_amount) sale_position_price,
                                 sum(opo.position_amount) sale_position_amount
                            from otc_trade_position_open opo
                           where opo.position_bs = '2'
                             and opo.account_type = '1'
                             and position_bs = '1'
                           group by opo.goods_code, opo.position_bs) s
            on (t.goods_code = s.goods_code)) q
  left outer join otc_goods r
    on (q.goods_code = r.goods_code)

 

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查詢方法同樣，就是條件變了一下，但是聯合查詢的商品名稱卻在上面一個裏面查詢不出來，而下面一個裏面顯示正常。分析緣由，nvl函數的問題，nvl(t.goods_code, s.goods_code) 前面一個查詢語句裏面，goods_code是取的s.goods_code,後面一個取的是t.goods_code.雖然值同樣，可是前面一個聯合查詢卻查詢不出來，有點詭異。

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解決方法：換成nvl2, 將上面代碼裏面的 nvl(t.goods_code,s.goods_code)換成nvl2(t.goods_code, t.goods_code, s.goods_code)上面存在的問題便可解決。