Sql 不存在行数据时返回零值

我的问题已经在前面讨论过了，但我似乎无法对我的查询应用任何解决方案来使其工作。非常感谢您的指导

下面我的当前查询返回此数据集：

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在过去的几天里，我读了很多关于NVL、COALESCE、FULL/LEFT/RIGHT-OUTER-JOIN、LEFT/RIGHT-JOIN、UNION-all等的文章，这些文章都没有案例陈述，我自己也尝试过解决它！你必须知道什么时候停下来问路。

首先，重新写下你的查询。使用视图或公共表表达式避免SELECT、GROUP BY和ORDER BY子句重复三次。您的查询变成：

WITH data AS (
    SELECT(CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
                WHEN time_dtm > SYSDATE -2 AND 
                     time_dtm < SYSDATE -1 THEN '1-2 days'
                WHEN time_dtm > SYSDATE -3 AND 
                     time_dtm < SYSDATE -2 THEN '2-3 days'
                WHEN time_dtm > SYSDATE -4 AND 
                     time_dtm < SYSDATE -3 THEN '3-4 days'
                WHEN time_dtm > SYSDATE -5 AND 
                     time_dtm < SYSDATE -4 THEN 'Closed'
           END) AS Age 
    FROM table_1 
    WHERE id IN (1,2,3)
)
SELECT Age, COUNT(*)
FROM data
GROUP BY Age
ORDER BY Age

完全不同的解决方案将涉及左外联接：

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在第二个示例中，您也可以不使用CTE，而对groups表使用嵌套的SELECT。很容易看出，如果您的需求发生变化，第二个示例在将来如何更容易发展。

感谢@Lukas回答我的问题。我尝试将数据作为&UNION ALL，但它没有将年龄识别为标识符。我还尝试了动态组&leftouterjoin，它返回了与我的原始查询相同的数据集，没有任何行。你还有什么建议吗？如果相关的话，我正在使用Toad for Oracle11.5。附言：动态群组很酷@ltran：我在第一次查询中出现语法错误，忘记了FROM子句。。。另外，在第二个查询中，我将1,2,3谓词中的t.id移到了一个子select中。这就是它不起作用的原因。让我知道，如果这有助于超级棒，他们都工作的待遇！谢谢你进一步简化了我的问题。我还没有足够的分数来投票，但我会在积分累积到@Lukas时投票。干杯，很高兴知道。你总是可以接受，没有必要的名誉去投票，我think@ltran：为什么-1？表1中未添加任何记录，计数应正确。。。

SELECT(CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
        WHEN time_dtm > SYSDATE -2 AND time_dtm < SYSDATE -1 THEN '1-2 days'
        WHEN time_dtm > SYSDATE -3 AND time_dtm < SYSDATE -2 THEN '2-3 days'
        WHEN time_dtm > SYSDATE -4 AND time_dtm < SYSDATE -3 THEN '3-4 days'
        WHEN time_dtm > SYSDATE -5 AND time_dtm < SYSDATE -4 THEN 'Closed'
        END) AS Age, 
    COUNT( * ) AS "Count" 
FROM table_1 
WHERE id IN (1,2,3)
GROUP BY (CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
        WHEN time_dtm > SYSDATE -2 AND time_dtm < SYSDATE -1 THEN '1-2 days'
        WHEN time_dtm > SYSDATE -3 AND time_dtm < SYSDATE -2 THEN '2-3 days'
        WHEN time_dtm > SYSDATE -4 AND time_dtm < SYSDATE -3 THEN '3-4 days'
        WHEN time_dtm > SYSDATE -5 AND time_dtm < SYSDATE -4 THEN 'Closed'
        END)
ORDER BY (CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
        WHEN time_dtm > SYSDATE -2 AND time_dtm < SYSDATE -1 THEN '1-2 days'
        WHEN time_dtm > SYSDATE -3 AND time_dtm < SYSDATE -2 THEN '2-3 days'
        WHEN time_dtm > SYSDATE -4 AND time_dtm < SYSDATE -3 THEN '3-4 days'
        WHEN time_dtm > SYSDATE -5 AND time_dtm < SYSDATE -4 THEN 'Closed'
        END)

  |  Age      |   Count   |
     0-1 day      300
     1-2 days     0
     2-3 days     6000
     3-4 days     100
     Closed       0

WITH data AS (
    SELECT(CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
                WHEN time_dtm > SYSDATE -2 AND 
                     time_dtm < SYSDATE -1 THEN '1-2 days'
                WHEN time_dtm > SYSDATE -3 AND 
                     time_dtm < SYSDATE -2 THEN '2-3 days'
                WHEN time_dtm > SYSDATE -4 AND 
                     time_dtm < SYSDATE -3 THEN '3-4 days'
                WHEN time_dtm > SYSDATE -5 AND 
                     time_dtm < SYSDATE -4 THEN 'Closed'
           END) AS Age 
    FROM table_1 
    WHERE id IN (1,2,3)
)
SELECT Age, COUNT(*)
FROM data
GROUP BY Age
ORDER BY Age

WITH data AS (
    SELECT(CASE WHEN time_dtm > SYSDATE -1 THEN '0-1 day'
                WHEN time_dtm > SYSDATE -2 AND 
                     time_dtm < SYSDATE -1 THEN '1-2 days'
                WHEN time_dtm > SYSDATE -3 AND 
                     time_dtm < SYSDATE -2 THEN '2-3 days'
                WHEN time_dtm > SYSDATE -4 AND 
                     time_dtm < SYSDATE -3 THEN '3-4 days'
                WHEN time_dtm > SYSDATE -5 AND 
                     time_dtm < SYSDATE -4 THEN 'Closed'
           END) AS Age 
    FROM table_1 
    WHERE id IN (1,2,3)

    -- The below will add one record for every desired Age group
    UNION ALL
    SELECT '0-1 day'  FROM DUAL UNION ALL
    SELECT '1-2 days' FROM DUAL UNION ALL
    SELECT '2-3 days' FROM DUAL UNION ALL
    SELECT '3-4 days' FROM DUAL UNION ALL
    SELECT 'Closed'   FROM DUAL
)
SELECT Age, COUNT(*) - 1 -- Subtract the extra record again
FROM data
GROUP BY Age
ORDER BY Age

-- Groups is a dynamic table that contains the date ranges and their "Age" label
WITH groups AS (
    SELECT SYSDATE -1 lower, SYSDATE upper, '0-1 day'  Age FROM DUAL UNION ALL
    SELECT SYSDATE -2      , SYSDATE -1   , '1-2 days'     FROM DUAL UNION ALL
    SELECT SYSDATE -3      , SYSDATE -2   , '2-3 days'     FROM DUAL UNION ALL
    SELECT SYSDATE -4      , SYSDATE -3   , '3-4 days'     FROM DUAL UNION ALL
    SELECT SYSDATE -5      , SYSDATE -4   , 'Closed'       FROM DUAL
)
SELECT g.Age, NVL(SUM(t.counter), 0)
FROM groups g

-- LEFT OUTER JOINing "table_1" to "groups" will ensure that every group
-- appears at least once in the result
LEFT OUTER JOIN (
  SELECT 1 counter, t.* FROM table_1 t WHERE t.id IN (1,2,3)
) t
ON  t.time_dtm >= g.lower
AND t.time_dtm <  g.upper
GROUP BY g.Age
ORDER BY g.Age