基于非空列的MySql内连接

Question

    I have Two tables :
    Table1, Table2

我必须编写一个SQL查询，该查询基于这些表上的<> 0条件，在三列上具有内部联接。我的情况是

    if(table1.ID != 0), then inner join on table1.ID = table2.ID else,

    if(table1.MemberID != 0), then inner join on table1.MemberID = table2.MemberID else,

    inner join on table1.PersonID = table2.PersonID

Answer 1

可以在join子句中使用条件语句(例如，大小写)。

select t1.*, t2.*
from table1 t1
inner join table2 t2 on 
            (case when 
                 t1.ID != 0 
                 then t1.ID =t2.Id
                 else
                 case when t1.MemberId !=0 
                      then t1.MemberId = t2.MemberId
                      else
                           t1.PersonId = t2.PersonId
                  end
            end)

请参阅SqlFiddle

Answer 2

这应该能行。

select * 
from Table1, Table2
where table1.Personid = table2.personId
and (((Table1.id != 0) and  (Table1.id = table2.Id))
or ((Table1.memberid != 0) and (Table1.memberid = table2.memberId)))