sql - Oracle UPDATE 使用包含 JOIN 的 SELECT 语句

Question

我正在将 H2 UPDATE/SELECT 语句移植到 Oracle，但遇到了无法诊断的语法问题。

我有 3 个表:Users、Cars 和 Trips。它们看起来像:

SELECT * FROM USERS;
+------------+----+--------+
|  USERNAME  | ID | CAR_ID |
+------------+----+--------+
| John.Smith |  1 |     5  |
| Abby.Smith |  2 |     6  |
+------------+----+--------+

SELECT * FROM CARS;
+----+--------+-------+
| ID |  MAKE  | COLOR |
+----+--------+-------+
|  5 | Subaru | Green |
|  6 | Honda  | Red   |
+----+--------+-------+

SELECT * FROM TRIPS;
+----+------------+---------+
| ID |  USERNAME  | MILEAGE |
+----+------------+---------+
|  8 | Abby.Smith |      87 |
|  9 | John.Smith |      23 |
+----+------------+---------+

但是，我们现在决定向 Trips 添加一个新列，并(仅)跟踪汽车型号而不是用户。作为中间结果，在删除 USERNAME 列之前，我试图实现:

+----+------------+---------+-----------+
| ID |  USERNAME  | MILEAGE | CAR_MODEL |
+----+------------+---------+-----------+
|  8 | Abby.Smith |      87 |     Honda |
|  9 | John.Smith |      23 |    Subaru |
+----+------------+---------+-----------+

我的(非功能性)声明如下所示:

WITH USER_MODELS AS
(SELECT USERNAME, MAKE FROM USERS JOIN CARS ON (USERS.CAR_ID = CARS.ID))
UPDATE TRIPS SET CAR_MODEL =
    SELECT MAKE FROM USER_MODELS
    WHERE TRIPS.USERNAME = USER_MODELS.USERNAME

但是，我收到的语法错误是:

UPDATE TRIPS SET CAR_MODEL =
*
ERROR at line 3:
ORA-00928: missing SELECT keyword

这让我大吃一惊。 SELECT 语句紧跟在 UPDATE 后面，该语句本身前面有一个 WITH 子句，该子句似乎包含格式正确的 SELECT .

Answer 1

可以做到，但是需要将WITH子句放在子查询中:

UPDATE TRIPS SET CAR_MODEL =
( WITH USER_MODELS AS
       (SELECT USERNAME, MAKE FROM USERS JOIN CARS ON (USERS.CAR_ID = CARS.ID))
  SELECT MAKE FROM USER_MODELS
   WHERE TRIPS.USERNAME = USER_MODELS.USERNAME
);