Unir dos tablas con diferentes valores clave

Tengo dos mesas:

tabla 1 

Name | AMOUNT  | TYPE

John | 20      |  TH 

Jill | 10      |  IU

Bill | 30      |  IK

John | 45      |  AL

Tabla 2

TYPE | DESC

88   | RENT

34   | ALIMONY

87   | TAX

56   | BEER

I have to join these tables. I know that TYPE 'TH' in table 1 corresponds to '88' in table 2. Similarly, IK corresponds to 87 and so on . But there isn't any reference table which says so which I could use for joining these . Is there any workaround for this ?

preguntado el 28 de mayo de 14 a las 14:05

Create a table with rows TH 88, IK 87 etc, if there isn't already one, and use two joins. -

4 Respuestas

If these are the only data contained on the tables you can create a new table, table3:

   TYPE 1| TYPE2

    88   | TH 

    34   | IU

    87   | IK

    56   | AL

Y prueba:

select Name,Amount,Type.table1,Type,table2 from  table1 inner join table3
on table1.Type=table3.Type2
inner join
table2 on table2.type=tabl3.type1

contestado el 28 de mayo de 14 a las 14:05

You don't mention DBMS but you should be able to use a derived table like:

select ...
from t1
join ( values ('TH',88),('IK',87) ) as a (x,y)
    on t1.type = a.x
join t2
    on a.y = t2.type

Es posible que tengas que hacer algo como:

join ( select ('TH',88) union all select ('IK',87) ) as a (x,y)

instead. But if this relationship exists, why don't create a table for it and insert the information?

contestado el 28 de mayo de 14 a las 14:05

Ok, this is a rather strange question because it is against the rules of relational databases. But you can fix it like this:

inner join Table2 on Table2.Type = 88 and Table1.Type = 'TH'

This you can do for each combination. But I suggest it would be better to add a new column with a reference to the id of the type.

contestado el 28 de mayo de 14 a las 14:05

If there exists some good reason for not creating a third table, you can write something like:

  SELECT
    ........
  FROM
    table1 a
  JOIN table2 b
  ON
    (
      CASE
        WHEN a.type='TH'
        THEN 88
        WHEN a.type='IK'
        THEN 87
      ...........
      END
    )
    =b.type

contestado el 28 de mayo de 14 a las 15:05

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