列名不明确，但使用“.”指定表

Question

当以下查询发送到我的数据库时：

SELECT statemachines.statemachinename, 
states.statename, 
actionhandlers.actionhandler, 
actions.value, actions.sourcename 
FROM actions, actionhandlers, states, statemachines 
INNER JOIN rules ON (actions.rule_id AND rules.rule_id) 
INNER JOIN actionhandlers ON (actions.actionhandler AND actionhandlers.actionhandler) 
INNER JOIN states ON (states.state_id AND actions.state_id) 
INNER JOIN statemachines ON (states.statemachinename AND statemachines.statemachinename) 
WHERE (rules.eventname = 'PIR') AND (statemachines.currentstate = states.state_id)

返回如下错误：

 android.database.sqlite.SQLiteException: ambiguous column name: statemachines.statemachinename (code 1): , while compiling:

我不知道该怎么做，我的所有其他查询都有效。

Answer 1

你使用了两次statemachines。一次在 JOIN 子句中，一次在 FROM 中。

说出其中一个：

...
FROM actions, actionhandlers, states, statemachines AS statemachines1
...

Answer 2

简化：FROM actions, actionhandlers, states, statemachines => FROM actions