将Oracle SQL Select转换为PostgreSQL select

Question

我有这条SQL语句:

SELECT ABX.ABX_APO_NUMBER,
       COUNT(A1.PROCESS_MODE) AS NUM_PLANNING,
       COUNT(A2.PROCESS_MODE) AS NUM_SETUP,
       COUNT(A3.PROCESS_MODE) AS NUM_OUTPUT
  FROM ABX, USER_INSTANCE U, ACTIVE_PROCESS A1,
       ACTIVE_PROCESS A2, ACTIVE_PROCESS A3
 WHERE U.ABX_APO_NUMBER (+) = ABX.ABX_APO_NUMBER
   AND A1.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A1.PROCESS_MODE (+)= 'PLANNING'
   AND A2.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A2.PROCESS_MODE (+) = 'SETUP'
   AND A3.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A3.PROCESS_MODE (+) = 'OUTPUT'
 GROUP BY ABX.ABX_APO_NUMBER

(+) 这个符号让PG出现了问题... 我可以直接删除它吗？如果要达到同样的效果，应该使用什么等价物Postgres才能理解呢？

- mainstringargs

Answer 1

以下是使用ANSI-92 JOIN语法重写的查询：

  SELECT a.abx_apo_number,
         COUNT(ap1.process_mode) AS NUM_PLANNING,
         COUNT(ap2.process_mode) AS NUM_SETUP,
         COUNT(ap3.process_mode) AS NUM_OUTPUT
     FROM ABX a
LEFT JOIN USER_INSTANCE u ON u.abx_apo_number = a.abx_apo_number
LEFT JOIN ACTIVE_PROCESS ap1 ON ap1.process_instance_number = u.instance_number
                            AND ap1.process_mode = 'PLANNING'
LEFT JOIN ACTIVE_PROCESS ap2 ON ap2.process_instance_number = u.instance_number
                            AND ap2.process_mode = 'SETUP'
LEFT JOIN ACTIVE_PROCESS ap3 ON ap3.process_instance_number = u.instance_number
                            AND ap3.process_mode = 'OUTPUT'
 GROUP BY a.abx_apo_number

(+)是Oracle特定的LEFT OUTER JOIN语法。要去掉它，需要为每个USER_INSTANCE.instance_number设置所有三个进程模式的值：PLANNING、SETUP和OUTPUT——省略任何一个，abx_apo_number在输出中将不会显示。

- OMG Ponies

Answer 2

不能仅仅去除它们！

(+)是旧版的OUTER JOIN符号。

例如：

...
  FROM USER_INSTANCE U, ACTIVE_PROCESS A1
 WHERE A1.PROCESS_INSTANCE_NUMBER (+) = U.INSTANCE_NUMBER
   AND A1.PROCESS_MODE (+)= 'PLANNING'
...

需要更改为

...
FROM USER_INSTANCE U
LEFT JOIN ACTIVE_PROCESS A1
     ON (     A1.PROCESS_INSTANCE_NUMBER = U.INSTANCE_NUMBER
          AND A1.PROCESS_MODE = 'PLANNING'
        )
...

- Peter Lang