What's the best way to handle one-to-one relationships in SQL? [closed]

Answer 1

I have an example working pretty well so far that fits your model:

I Have Charlie and Bravo Tables Having the Foreign Key alpha_id from Alpha. Like your first example, except alpha is not the Primary Key, bravo_id and charlie_id are.

I use alpha_id on every table I need to address to those entities, so, to avoid a SQL that may cause some delay researching both Bravo and Charlie to find which one Alpha is, I created a AlphaType table and on Alpha table I have its id (alpha_type_id) as foreign key. That way I can know in a programmatic way which AlphaType I am dealing with without Joining tables that may have zillions of records. in tSQL:

// For example sake lets think Id as a CHAR.
// and pardon me on any mistake, I dont have the exact code here,
// but you can get the idea

SELECT 
  (CASE alpha_type_id
    WHEN 'B' THEN '[Bravo].[Name]'
    WHEN 'C' THEN '[Charlie].[Name]'
    ELSE Null
  END)
FROM ...