Question

我有带日志的表，当他们请求时->它们将可见状态更改为true。问题是我不需要更新已经看到的行，只需返回它们。有办法吗？

logs
id | seen
1  | false
2  | true

UPDATE logs as new
SET seen=true 
FROM (SELECT * FROM logs WHERE seen  is not null LIMIT 5) as old
WHERE new.id = old.id //if i add here "AND old.seen=false" then nothing will return
RETURNING old.seen

Answer 1

您的子查询应该过滤掉“看不见的”记录，并且也不需要返回所有列：

(SELECT id FROM logs WHERE NOT seen LIMIT 5)

这将返回log表中最多5条记录，其中seen等于false的ID。

更新后的解决方案如下：

UPDATE logs
SET seen = true
FROM (SELECT id FROM logs WHERE NOT seen LIMIT 5) AS unseen
WHERE logs.id = unseen.id
RETURNING id; -- Returning `seen` would only return false. `id` is more useful, no?

Postresql更新有限的行并返回旧值

1 个答案: