即使一个表中没有数据，也可以从多个表中选择数据 [英] Select data from multiple tables even if there no data in one table

问题描述

你好
即使没有其他表的数据，我怎么也能从2个表中获取数据
例如:fathers表具有column_id，name列.sons表具有column_id，name列

此查询
从父亲f，儿子​​s中选择f.father_id，f.name，s.name
其中f.father_id = s.father_id和father_id = @ parameter

我想从这些表中获取数据，如果存在与父表相关的father_id，并且不作为空或任何空字符串

如果子表中没有数据，就这样
父亲编号，父亲姓名，儿子姓名
1个templ null
2约翰·空

感谢all

hello
how can i get data from 2 tables even if there is no data into other table
ex: fathers table has columns father_id,name .. sons table has columns son_id ,name

this query
select f.father_id,f.name,s.name from fathers f,sons s
where f.father_id=s.father_id and father_id=@parameter

i want to get data from these tables if exists related father_id into son table and if not get it as null or any empty string

like this if no data into son table
father_id,fathername ,sonname
1 templ null
2 john null

thanks all

推荐答案

如果另一个表中没有匹配的记录，请使用外部联接获取记录.请参阅: http://msdn.microsoft.com/en-us/library/ms187518.aspx [ ^ ]

因此，在您的声明中，类似以下内容:

Use outer join to get records if there''s no matching record in another table. See: http://msdn.microsoft.com/en-us/library/ms187518.aspx[^]

So in you statement, something like:

select f.father_id,f.name,s.name 
from fathers f left outer join sons s
on f.father_id=s.father_id

如果要限制使用father_id，则类似:

If you want to restrict using father_id, something like:

SELECT f.father_id,
       f.name,
       s.name
FROM  fathers f LEFT OUTER JOIN sons s
ON    f.father_id = s.father_id
WHERE f.father_id = @father_id 

如果有的话，这应该带来一个全子的单亲父亲.

That should bring a single father with all sons, if any exist

使用左外部联接建立您的查询.

Use left outer join to build your query.

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