最终总和的空值 使用MATCH_RECOGNIZE时加倍

Question

当我运行以下代码时，我希望b1和b2相等，但是，b2是双倍的。我做错了什么吗？这是数据库中的错误吗？我们正在运行Oracle 12c(12.2.0.1.0).

WITH TBL AS
(
SELECT 1 a, 1 b FROM DUAL UNION ALL
SELECT 1 a, 2 b FROM DUAL UNION ALL
SELECT 1 a, 3 b FROM DUAL UNION ALL
SELECT 1 a, 4 b FROM DUAL
)
SELECT
*
FROM
TBL
MATCH_RECOGNIZE
(
PARTITION BY
a
ORDER BY
b
MEASURES
FINAL SUM(b) b1,
NULLIF(FINAL SUM(b), 0) b2
ALL ROWS PER MATCH WITH UNMATCHED ROWS
AFTER MATCH SKIP PAST LAST ROW
PATTERN
(C*)
DEFINE
C AS B > 0
) mr

结果：

| A | B | B1 | B2 |
|---|---|----|----|
| 1 | 1 | 10 | 20 |
| 1 | 2 | 10 | 20 |
| 1 | 3 | 10 | 20 |
| 1 | 4 | 10 | 20 |

Answer 1

当我将其转换为逻辑等效物并且它工作正常时，问题似乎出在NULLIF上，CASE WHEN expr1 = expr 2 THEN NULL ELSE expr1 END

WITH TBL AS
(
SELECT 1 a, 1 b FROM DUAL UNION ALL
SELECT 1 a, 2 b FROM DUAL UNION ALL
SELECT 1 a, 3 b FROM DUAL UNION ALL
SELECT 1 a, 4 b FROM DUAL
)
SELECT
*
FROM
TBL
MATCH_RECOGNIZE
(
PARTITION BY
a
ORDER BY
b
MEASURES
FINAL SUM(b) b1,
CASE WHEN FINAL SUM(b)=0 THEN NULL ELSE FINAL SUM(b) END b2
ALL ROWS PER MATCH WITH UNMATCHED ROWS
AFTER MATCH SKIP PAST LAST ROW
PATTERN
(C*)
DEFINE
C AS B > 0
) mr 

结果

| A | B | B1 | B2 |
|---|---|----|----|
| 1 | 1 | 10 | 10 |
| 1 | 2 | 10 | 10 |
| 1 | 3 | 10 | 10 |
| 1 | 4 | 10 | 10 |