Question

我有两张桌子：

CREATE TABLE  "status" (
    "id" integer NOT NULL PRIMARY KEY,
    "created_at" datetime NOT NULL,    
    "updated_at" datetime NOT NULL);


CREATE TABLE "device" (
    "id" integer NOT NULL PRIMARY KEY,
    "created_at" datetime NOT NULL,
    "updated_at" datetime NOT NULL,
    "last_status_object_id" integer REFERENCES "status" ("id"));

在表“device”中，last_status_object_id引用status.id。

我想删除“last_status_object_id”未引用的所有状态行。我似乎无法弄清楚如何实现这一目标。任何人都可以帮助我吗？

Answer 1

DELETE
    status
FROM
    status
    LEFT JOIN device ON (status.id = last_status_object_id)
WHERE
    device.id IS NULL

Answer 2

delete from status
where id not in (select last_status_object_id
                            from device);

我们转到sqlfiddle

中的演示

Answer 3

我想删除“last_status_object_id”未引用的所有状态行。

表达方式的一种简单方法是使用NOT EXISTS：

DELETE FROM 
    status
WHERE
    NOT EXISTS (SELECT * FROM device WHERE last_status_object_id = status.id)

删除一个表中未被另一个表引用的所有行

3 个答案: