Question

I have a mapping table that can hold IDs from the same table.

For example I have :

Variables ( Table )
Values ( Table)
Variables_Values ( Mapping table )

The mapping table has the following fields :

VariableID
To_VariableID
To_ValueID

So it is possible for a row to have two variable IDs, or a variable ID and a value ID.
It is always a pair, so there cannot be two variable IDs and a value ID at the same time.

Now, in the Variables and Values tables, there is a Name field, so variables and values also have names.

I want to create a query that will display the names based on the IDs in the mapping table, but I am not sure how.

Right now I have a query that returns results that look like this :

VariableName To_VariableID To_ValueID

I would like to display VariableName_2, ValueName instead of To_VariableID To_ValueID.

Is there a technique for this?
Could it be a combination of the following queries?

SELECT map.ID, map.TransitionID, variable.Name
FROM Variables AS variable INNER JOIN Mapping AS map 
ON variable.VariableID = map.VariableID

SELECT variable.VariableID, variable.Name
FROM Variable AS variable
WHERE variable.VariableID IN ( SELECT map.To_VariableID FROM Mapping AS map)

SELECT value.Name
FROM Values AS value
WHERE value.ValueID IN ( SELECT map.To_ValueID FROM Mapping AS map)

Thank you.

Answer 1

It was as simple as this :

SELECT map.Transition_Set_Variable_ID, 
       map.Transition_ID,
       variable.Name,
       variable2.Name,
       value.Name
FROM Variables AS variable 
  INNER JOIN Mapping AS map ON variable.VariableID = map.VariableID
  LEFT JOIN Variables AS variable2 ON map.To_VariableID = variable2.VariableID
  LEFT JOIN Values AS value ON tsv.To_ValueID = value.ValueID
ORDER BY map.TransitionID, variable.VariableID