Oracle

Question

我希望我的 Oracle SQL 输出在查询 returns 没有结果时显示 'No Rows Found'。

我正在尝试使用 NVL 函数，但我收到一条错误消息

'ERROR at line 21: ORA-00907: missing right parenthesis'

SELECT NVL((
            SELECT TO_CHAR(CHGDATE, 'yyyy-mm')
                ,CHGFIELD
                ,DBNAME
                ,COUNT(*)
            FROM APPCHANGEHIST A
                ,DATABASEFIELD D
            WHERE A.CHGFIELD = D.FIELDNUM
                AND trunc(CHGDATE) BETWEEN add_months(to_date(to_char((sysdate - to_char(sysdate, 'dd') + 1), 'dd-mon-yyyy')), - 1)
                    AND to_date(to_char((sysdate - to_char(sysdate, 'dd')), 'dd-mon-yyyy'))
                AND CHGFIELD = 79
                AND OLDVALUE IS NOT NULL
                AND EXISTS (
                    SELECT 1
                    FROM USERPROF
                    WHERE USERID = A.CHGREQUESTOR
                    )
            GROUP BY TO_CHAR(CHGDATE, 'yyyy-mm')
                ,CHGFIELD
                ,DBNAME
            ORDER BY 1
                ,4 DESC
            ), "No Rows");

当我运行这个声明没有 NVL

时我没有问题

SELECT TO_CHAR(CHGDATE, 'yyyy-mm')
                ,CHGFIELD
                ,DBNAME
                ,COUNT(*)
            FROM APPCHANGEHIST A
                ,DATABASEFIELD D
            WHERE A.CHGFIELD = D.FIELDNUM
                AND trunc(CHGDATE) BETWEEN add_months(to_date(to_char((sysdate - to_char(sysdate, 'dd') + 1), 'dd-mon-yyyy')), - 1)
                    AND to_date(to_char((sysdate - to_char(sysdate, 'dd')), 'dd-mon-yyyy'))
                AND CHGFIELD = 79
                AND OLDVALUE IS NOT NULL
                AND EXISTS (
                    SELECT 1
                    FROM USERPROF
                    WHERE USERID = A.CHGREQUESTOR
                    )
            GROUP BY TO_CHAR(CHGDATE, 'yyyy-mm')
                ,CHGFIELD
                ,DBNAME
            ORDER BY 1
                ,4 DESC

Answer 1

好的，在高层次上，您可以使用以下模式：

WITH results AS
(
  SELECT *
  FROM dual d
  WHERE d.dummy = 'Y'
)
SELECT *
FROM results
UNION ALL
SELECT 'No Rows Found'
FROM dual
WHERE NOT EXISTS (SELECT 'X'
                  FROM results);

您可以通过更改 'X' 和 'Y' 之间的 WITH 子句中的值来玩这个。在您的查询中，您只需将 WITH 子句中的 SELECT 替换为您的查询即可。

Oracle - 查询 returns 无结果时显示 'No Rows'

Oracle - Display 'No Rows' when query returns no results

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