Oracle Syntax to Postgres帮助

Question

我正在尝试从Oracle转换以下代码：

CREATE VIEW PLANNED AS
SELECT ASP.ASP_SPACE_NM,
       SUM(MO.MO_TKR_TOTAL_OFF_SCHEDULED) "TOTAL_PLANNED"
  FROM OBJECTIVE MO, SPACE ASP
 WHERE ASP.ASP_SPACE_NM = MO.ASP_SPACE_NM (+)
   AND MO.MO_MSN_CLASS_NM = 'EPIC'
 GROUP BY ASP.ASP_SPACE_NM

敬波斯格雷斯。

这里有两行代码让我感到困惑：

   SUM(MO.MO_TKR_TOTAL_OFF_SCHEDULED) "TOTAL_PLANNED"

这个和这个一样吗？

   SUM(MO.MO_TKR_TOTAL_OFF_SCHEDULED) AS TOTAL_PLANNED

我不知道这行中的(+)是什么意思：

 WHERE ASP.ASP_SPACE_NM = MO.ASP_SPACE_NM (+)

Answer 1

这是Oracle特有的LEFT JOIN语法的老派。您希望将其替换为：

CREATE VIEW PLANNED AS
   SELECT s.asp_space_nm,
          SUM(o.mo_tkr_total_off_scheduled) 'total_planned'
     FROM SPACE s
LEFT JOIN OBJECTIVE o ON o.asp_space_nm = s.asp_space_nm 
                     AND o.mo_msn_class_nm = 'EPIC'
 GROUP BY s.asp_space_nm

参考资料：

• Oracle LEFT JOIN

Answer 2

+表示一个(edit: left)外部联接。

和

SUM(MO.MO_TKR_TOTAL_OFF_SCHEDULED) "TOTAL_PLANNED"

确实很可能与

SUM(MO.MO_TKR_TOTAL_OFF_SCHEDULED) as "TOTAL_PLANNED"

如果我没记错的话，PostgreSQL实际上也不需要as (尽管在我看来，它让它变得更加明确)。

你可以在Postgresql wiki上看看下面的页面，了解更多的区别：Oracle to Postgres conversion。