sql - 如何使用分析函数填充缺失值？

Question

我想从我的数据集中填充缺失的空值。我有一个这样的数据集

+---------------------+------+-------------+
| ORDER_DATE          | SHOP | SALESPERSON |
+---------------------+------+-------------+
| 14/04/2017 04:44:27 | A    | MIKE        |
+---------------------+------+-------------+
| 14/04/2017 04:44:55 | A    |             |
+---------------------+------+-------------+
| 14/04/2017 04:45:07 | A    | TIM         |
+---------------------+------+-------------+
| 14/04/2017 04:45:30 | A    |             |
+---------------------+------+-------------+
| 14/04/2017 04:45:43 | B    |             |
+---------------------+------+-------------+
| 14/04/2017 04:46:13 | B    | JOHN        |
+---------------------+------+-------------+
| 14/04/2017 04:46:28 | B    |             |
+---------------------+------+-------------+
| 14/04/2017 04:58:32 | C    |             |
+---------------------+------+-------------+
| 14/04/2017 04:58:41 | C    | MELINDA     |
+---------------------+------+-------------+

我喜欢使用商店内的空值之前的第一个找到的值来填充按商店划分的销售员信息。我试过了，但这不会产生正确的结果(如下)。如何解决这个问题？

CREATE TABLE SALES (
ORDER_DATE DATE, 
SHOP VARCHAR2(30 CHAR), 
SALESPERSON VARCHAR2(30 CHAR)
)
;

REM INSERTING INTO SALES
SET DEFINE OFF;
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:44:27','DD/MM/YYYY HH24:MI:SS'),'A','MIKE');
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:44:55','DD/MM/YYYY HH24:MI:SS'),'A',NULL);
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:45:07','DD/MM/YYYY HH24:MI:SS'),'A','TIM');
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:45:30','DD/MM/YYYY HH24:MI:SS'),'A',NULL);
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:45:43','DD/MM/YYYY HH24:MI:SS'),'B',NULL);
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:46:13','DD/MM/YYYY HH24:MI:SS'),'B','JOHN');
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:46:28','DD/MM/YYYY HH24:MI:SS'),'B',NULL);
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:58:32','DD/MM/YYYY HH24:MI:SS'),'C',NULL);
INSERT INTO SALES (ORDER_DATE,SHOP,SALESPERSON) VALUES (TO_DATE('14/04/2017 04:58:41','DD/MM/YYYY HH24:MI:SS'),'C','MELINDA');
COMMIT;

SELECT * FROM SALES ORDER BY SHOP, ORDER_DATE;

SELECT ORDER_DATE,
       SHOP,
       SALESPERSON,
       /*tried two approaches*/
       /*does not produce a correct result set*/
       LAST_VALUE(SALESPERSON) IGNORE NULLS OVER (PARTITION BY SHOP
                   ORDER BY ORDER_DATE RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) AS LAST_VALUE_1,
       /*this also does not solve this*/            
       LAST_VALUE(SALESPERSON) IGNORE NULLS OVER(PARTITION BY SHOP
                  ORDER BY ORDER_DATE ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING) AS LAST_VALUE_2
FROM SALES ;

正确的结果集是:

+---------------------+------+-------------+--------------------+
| ORDER_DATE          | SHOP | SALESPERSON | SALESPERSON_FILLED |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:44:27 | A    | MIKE        |  MIKE              |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:44:55 | A    |             |  MIKE              |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:45:07 | A    | TIM         |  TIM               |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:45:30 | A    |             |  TIM               |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:45:43 | B    |             |                    |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:46:13 | B    | JOHN        |  JOHN              |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:46:28 | B    |             |  JOHN              |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:58:32 | C    |             |                    |
+---------------------+------+-------------+--------------------+
| 14/04/2017 04:58:41 | C    | MELINDA     |  MELINDA           |
+---------------------+------+-------------+--------------------+

Answer 1

你非常接近。
尝试这个:

SELECT ORDER_DATE,
       SHOP,
       SALESPERSON,

       LAST_VALUE(SALESPERSON) IGNORE NULLS OVER 
            (PARTITION BY SHOP ORDER BY ORDER_DATE ) AS LAST_VALUE_1

FROM SALES
order by shop, order_date;

ORDER_DA SHOP                           SALESPERSON                    LAST_VALUE_1                  
-------- ------------------------------ ------------------------------ ------------------------------
17/04/14 A                              MIKE                           MIKE                          
17/04/14 A                                                             MIKE                          
17/04/14 A                              TIM                            TIM                           
17/04/14 A                                                             TIM                           
17/04/14 B                                                                                           
17/04/14 B                              JOHN                           JOHN                          
17/04/14 B                                                             JOHN                          
17/04/14 C                                                                                           
17/04/14 C                              MELINDA                        MELINDA                       

9 rows selected.