postgresql - 如何连接两个查询结果？

Question

我想在某个时间跨度内检索所有 ID。然而，时间戳存储在不同的表中：

Table A has column  my_id
Table B has columns my_id, timestamp

我想要类似的东西

SELECT
  id,
  time
FROM
  (SELECT my_id AS id FROM A) q1,
  (SELECT timestamp AS time FROM B WHERE my_id = id) q2
;

但是我怎样才能id在不同的子查询中得到值呢？这个问题有一个优雅的解决方案吗？

score 1 · Accepted Answer

我看到在第二个子查询中，您尝试链接两个表：

(SELECT my_id AS id FROM A) q1,
(SELECT timestamp AS time FROM B WHERE my_id = id) q2

如果两个 id 必须相等：

SELECT a.my_id as id, b.timestamp as time
FROM A a
JOIN B b ON (a.my_id = b.my_id);

我希望这有帮助。

score 1 · Accepted Answer

更简单：

SELECT my_id AS id, b.my_ts
FROM   a
JOIN   b USING (my_id);

引用标识符也使其区分大小写，而未引用的名称总是折叠为小写。

2 回答 2