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: msdn.microsoft/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: msdn.microsoft/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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即使一个表中没有数据,也可以从多个表中选择数据
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