创建一个合并行的 SQL 查询

Question

我有一个表格，用于存储打开和关闭订单的日期。类似这样：

id	orderID	status	date
1	1	opened	2020-01-01
2	1	closed	2020-01-05
3	2	opened	2020-01-02

我需要一个返回以下结果的 SQL 查询：

orderId	openedDate	closedDate
1	2020-01-01	2020-01-05
2	2020-01-02	NULL

这是我尝试过的：

SELECT
orderId,
CASE WHEN status = 'opened' THEN date END AS openedDate,
CASE WHEN status = 'closed' THEN date END AS closedDate

FROM
orders

GROUP BY
orderId;

但我没有得到想要的结果。

Answer 1

您应该得到一个语法错误，因为select 列与group by 不一致。使用聚合：

SELECT orderId,
       MAX(CASE WHEN status = 'opened' THEN date END) AS openedDate,
       MAX(CASE WHEN status = 'closed' THEN date END) AS closedDate
FROM orders
GROUP BY orderId;