Question

我在下面有这个mysql查询。

UPDATE data_records
  INNER JOIN doors
  ON (sensors.gateway_id = doors.id)
  INNER JOIN data_records
  ON (data_records.sensor_id = sensors.id)
SET data_records.value=1
WHERE doors.addr='FFA'

我不知道导致错误Lookup Error - MySQL Database Error: Not unique table/alias: 'data_records'的原因。我的数据库中显然有data_records表。

Answer 1

您有> <some magic command> some context的两个联接。我想你打算：

data_records

您的查询引用UPDATE data_records dr INNER JOIN sensors s ON dr.sensor_id = s.id INNER JOIN doors d ON s.gateway_id = d.id SET dr.value = 1 WHERE d.addr = 'FFA';但未在sensors子句中定义。

另请注意，我添加了表别名，因此查询更容易编写和阅读。

Answer 2

您不是加入传感器，而是两次数据_recods

UPDATE data_records
INNER JOIN doors   ON (sensors.gateway_id = doors.id)
INNER JOIN sensors ON (data_records.sensor_id = sensors.id)
SET data_records.value=1
WHERE doors.addr='FFA'

Answer 3

您犯了一个错误，并使用了data_records两次而不是sensors表，或者您只是想将第二个data_records别名为sensors。无论哪种方式都是错误的。

第一个选项：

UPDATE data_records
  INNER JOIN doors
  ON (sensors.gateway_id = doors.id)
  INNER JOIN sensors
  ON (data_records.sensor_id = sensors.id)
SET data_records.value=1
WHERE doors.addr='FFA'

第二个：

UPDATE data_records
  INNER JOIN doors
  ON (sensors.gateway_id = doors.id)
  INNER JOIN data_records sensors
  ON (data_records.sensor_id = sensors.id)
SET data_records.value=1
WHERE doors.addr='FFA'

造成什么原因＆＃34;不是唯一的表/别名＆＃34; mysql中的错误？

3 个答案: