如何使用联接连接多个表？

Question

我正在尝试加入多个表并获取数据。但是我得到了重复的数据。我怎么解决这个问题？任何帮助。

select reliability.id,
reliability.type, 
header_id, 
header_name, 
parents.parent, 
namestates.namestate,
probabilities.probabilities
from reliability 

inner join headers
on reliability.id = headers.reliability_id 

inner join parents
on parents.reliability_id = reliability.id 

inner join definitions
on definitions.reliability_id = reliability.id

inner join namestates
on namestates.definition_id = definitions.id

inner join probabilities
on probabilities.definition_id = definitions.id

group by namestates.namestate,
probabilities.probabilities;

​

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Answer 1

请用左联接..。

select reliability.id,
reliability.type, 
header_id, 
header_name, 
parents.parent, 
namestates.namestate,
probabilities.probabilities
from reliability 

left join headers on reliability.id = headers.reliability_id 

left join parents on parents.reliability_id = reliability.id 

left join definitions on definitions.reliability_id = reliability.id

left join namestates on namestates.definition_id = definitions.id

left join probabilities on probabilities.definition_id = definitions.id

group by namestates.namestate, probabilities.probabilities;