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Databases

Ben Os
Ben Os
20,008 Points
Posted by Ben Os
Ben Os
20,008 Points

One to one table relationships: I'm not sure I understand how it is best to make the link

Is it true to say for one-to-one relation ?

Say we have 2 tables that shares the same column (like "media_id") which is represented in a column of its own;

For example, say we have 2 media tables, each with 3 items. One deals with films and the other with T.V series. Besides them we also have an "media_id" tables that links them:

film id - 1,2,3 ... T.V series id - 1,2,3 ... id table: 1,2,3,4,5,6 (the 4,5,6 are actually the T.V series 1,2,3).

1 Answer

Simon Coates
Simon Coates
28,694 Points
Simon Coates
Simon Coates
28,694 Points

both table will typically have an id Field. But one table has another field that it the id of the other table. so given table A and B. A will have an id field. B will have an id field (or a primary key). But one (let's say B), will have a field called B.a_id (that has to contain an id contained in the other table). This covers one to one (provided you don't have multiple mappings) and one to many. Many to many requires use of a junction table (which just applies the one-to-many technique twice).