Question

如何将这两个查询合并为一个？首先，我从id

中选择doorbots

select id --> 2576673
from doorbots 
where device_id = '38d269cf5d1f';

然后我使用此id从id表中选择dings

select id 
from dings 
where doorbot_id = 2576673 and deleted_at is NULL;

如何将这两个查询合并为一个？

Answer 1

使用in语句，您可以询问您想要的特定ID。

试试这个： -

select id 
from dings 
where doorbot_id in (select id 
from doorbots 
where device_id = '38d269cf5d1f')and deleted_at is NULL;

Answer 2

如果两个表都具有

之类的关系，则可以使用左连接或连接来组合它

SELECT d.id 
FROM dings d 
LEFT JOIN doorbots ON dbs dbs.id = d.doorbot_id 
WHERE d.deleted_at IS NULL AND dbs.device_id = '38d269cf5d1f';

SELECT d.id 
    FROM dings d 
    JOIN doorbots ON dbs dbs.id = d.doorbot_id 
    WHERE d.deleted_at IS NULL AND dbs.device_id = '38d269cf5d1f';

或者像这样

SELECT id 
FROM dings 
WHERE id IN (
    SELECT id 
    FROM doorbots 
    WHERE device_id = '38d269cf5d1f'
) AND d.deleted_at IS NULL;

Answer 3

你只需要更换＆＃34; 2576673＆＃34;在您的第一个查询的第二个查询中，括号括起来。

Answer 4

您可以通过树方式获得相同的结果，但仍然使用 IN，EXISTS 和 JOIN 进行单个查询。

使用：

SELECT id
FROM dings
WHERE doorbot_id IN
  (SELECT id
  FROM doorbots
  WHERE device_id = '38d269cf5d1f')
AND deleted_at IS NULL;

使用EXISTS：

SELECT id
FROM dings
WHERE doorbot_id EXISTS
  (SELECT 1
  FROM doorbots
  WHERE dings.doorbot_id =id and device_id = '38d269cf5d1f')
AND deleted_at IS NULL;

使用加入：

SELECT dings.id
FROM doorbots
JOIN dings
ON doorbots.id = dings.doorbot_id
WHERE doorbots.device_id = '38d269cf5d1f'
AND dings.deleted_at IS NULL;

Answer 5

您可以通过多种方式实现相同目标。使用JOIN，EXISTS或IN。 EXISTS和IN都使用子查询。所以我建议你去JOIN。你可以这样做：

SELECT d.id
FROM dings d
INNER JOIN doorbots db ON d.doorbot_id=db.id
WHERE db.device_id='38d269cf5d1f' AND d.deleted_at IS NULL

如何使用join将两个查询合并为一个？

5 个答案: