用于计数的嵌套计数查询的 SQL 语法问题？

Question

对于以下查询，我在 Oracle SQL Developer 中遇到了缺少表达式的错误， 有人可以帮我解决这个问题。

  SELECT COUNT(DISTINCT SEC.ERROR_GROUP_ID),
  COUNT(DISTINCT SEC_DET.ERROR_GROUP_ID),
  COUNT(DISTINCT MB.ERROR_GROUP_ID),
  COUNT(DISTINCT OD.ERROR_GROUP_ID),
  SELECT COUNT(DISTINCT SEC_SCH.ERROR_GROUP_ID)
   FROM SCHEMA.SECURITY SEC
    LEFT OUTER JOIN SCHEMA.SECURITY_SCHEDULE SEC_SCH
     ON SEC.MSD_SECURITY_ID     =SEC_SCH.MSD_SECURITY_ID
    WHERE SEC.MSD_SECURITY_ID IN
      ( SELECT DISTINCT main.MSD_SECURITY_ID
         FROM SCHEMA2.Positions main
          WHERE main.QUANTITY != 0
          AND systimestamp    >= main.eff_from_dt
          AND main.eff_to_dt   > systimestamp
          AND systimestamp    >= main.asrt_from_dt
          AND main.asrt_to_dt  > systimestamp
     ) 

FROM SCHEMA.SECURITY SEC
JOIN SCHEMA.SECURITY_DETAIL SEC_DET
ON SEC.MSD_SECURITY_ID = SEC_DET.MSD_SECURITY_ID
LEFT OUTER JOIN SCHEMA.MUNI_BOND MB
ON SEC.MSD_SECURITY_ID=MB.MSD_SECURITY_ID
LEFT OUTER JOIN SCHEMA.OPTION_DETAIL OD
ON SEC.MSD_SECURITY_ID =OD.MSD_SECURITY_ID
WHERE SEC.MSD_SECURITY_ID IN
  ( SELECT DISTINCT main.MSD_SECURITY_ID
  FROM SCHEMA2.Positions main
  WHERE main.QUANTITY != 0
  AND systimestamp    >= main.eff_from_dt
  AND main.eff_to_dt   > systimestamp
  AND systimestamp    >= main.asrt_from_dt
  AND main.asrt_to_dt  > systimestamp
  ) ;

错误

ORA-00936: 缺少表达式 00936. 00000 - “缺少表达式” *原因：
*行动： 行错误：365 列：3

Answer 1

子查询必须用括号括起来。添加它们后，Oracle 应该停止抱怨。

Answer 2

子查询确实需要放在括号中。子查询可能只使用COUNT(DISTINCT) 而不是嵌套子查询来编写：

SELECT COUNT(DISTINCT SEC.ERROR_GROUP_ID),
       COUNT(DISTINCT SEC_DET.ERROR_GROUP_ID),
       COUNT(DISTINCT MB.ERROR_GROUP_ID),
       COUNT(DISTINCT OD.ERROR_GROUP_ID),
       (SELECT COUNT(DISTINCT SEC_SCH.ERROR_GROUP_ID)
        FROM SCHEMA.SECURITY SEC LEFT OUTER JOIN
             SCHEMA.SECURITY_SCHEDULE SEC_SCH
             ON SEC.MSD_SECURITY_ID = SEC_SCH.MSD_SECURITY_ID
         WHERE SEC.MSD_SECURITY_ID IN ( <values>)  
        )  . . .

请注意，这与您的查询有非常小的语义差异。这不计算 NULL 值，而您的版本计算在内。您可以通过以下方式获得相同的语义：

       (SELECT COUNT(DISTINCT SEC_SCH.ERROR_GROUP_ID) + MAX(CASE WHEN SEC_SCH.ERROR_GROUP_ID IS NULL THEN 1 ELSE 0 END)
        FROM SCHEMA.SECURITY SEC LEFT OUTER JOIN
             SCHEMA.SECURITY_SCHEDULE SEC_SCH
             ON SEC.MSD_SECURITY_ID = SEC_SCH.MSD_SECURITY_ID
         WHERE SEC.MSD_SECURITY_ID IN ( <values>)  
        )  . . .

为此目的使用子查询是不寻常的。我想知道您是否可以使用分析函数。