Given 3 tables. How can I choose the right join if two cases were possible.

Table1

Table2

Table3

In the result I need the CustomerID-intern with the assigned address of it. In Table1 there can only be filled 1 field either CustomerID-extern or CustomerID-intern.

Thank you.

CodePudding user response：

You can use two left outer joins to match rows in the third table accordind to the direct codes or the translation codes in the second table. For example:

select a.Article, c.*  
from table1 a
left join table2 b on a.CustomerID_extern = b.CustomerID_extern
left join table2 c on c.CustomerID_intern = a.CustomerID_intern
                   or c.CustomerID_intern = b.CustomerID_intern