如何在SQL中透视

Question

我有一个要透视的桌子。我可以部分实现我想要的。我需要帮助才能完成

我的基本表

+-------------+----------+-------------+
| WorkOrderID | STEP_NBR | STEP_STATUS |
+-------------+----------+-------------+
| AA100       |        0 | C           |
| AA100       |        1 | W           |
| AA100       |        2 | W           |
| AA200       |        0 | W           |
| AA200       |        1 | W           |
| AA300       |        0 | C           |
| AA300       |        1 | C           |
+-------------+----------+-------------+

我想要的输出

+-------------+--------+--------+--------+
| WorkOrderID | Step_0 | Step_1 | Step_2 |
+-------------+--------+--------+--------+
| AA100       | C      | W      | W      |
| AA200       | W      | W      |        |
| AA300       | C      | C      |        |
+-------------+--------+--------+--------+

我得到的输出

+-------------+--------+--------+--------+
| WorkOrderID | Step_0 | Step_1 | Step_2 |
+-------------+--------+--------+--------+
| AA100       | C      | null   | null   |
| AA100       | null   | W      | null   |
| AA100       | null   | null   | W      |
| AA200       | W      | null   | null   |
| AA200       | null   | W      | null   |
| AA300       | C      | null   | null   |
| AA300       | null   | C      | null   |
+-------------+--------+--------+--------+

我的查询

SELECT WorkOrderID, 
(CASE WHEN STEP_NBR = 0 THEN STEP_STATUS ELSE NULL END) AS Step_0,
(CASE WHEN STEP_NBR = 1 THEN STEP_STATUS ELSE NULL END) AS Step_1,
(CASE WHEN STEP_NBR = 2 THEN STEP_STATUS ELSE NULL END) AS Step_2
FROM Table1

如何摆脱多个WorkOrderId。我只需要每个WorkOrderId 1行

db-fiddle

Answer 1

您只需要聚合：

SELECT WorkOrderID, 
       MAX(CASE WHEN STEP_NBR = 0 THEN STEP_STATUS END) AS Step_0,
       MAX(CASE WHEN STEP_NBR = 1 THEN STEP_STATUS END) AS Step_1,
       MAX(CASE WHEN STEP_NBR = 2 THEN STEP_STATUS END) AS Step_2
FROM Table1
GROUP BY WorkOrderID;

ELSE NULL是多余的，因此我将其删除。