Question

I have the following structure for my project and developer program:

developer table
id
developer name
etc...

project table
id
project name
etc...

developer _project table
???

Because a developer can be in multiple projects and a projects can have multiple developer I have to create a new table but from what I read is they don’t tell what id should I use.

If I use an id auto increment + user_id + project_id will I have duplicate since the id is the primary key?

Answer 1

Use a unique combined key:

CREATE TABLE `developer_project` (
 developer_id INT(10) UNSIGNED /* etc... */,
 project_id INT(10) UNSIGNED /* etc... */,
 PRIMARY KEY dev_project (developer_id, project_id)
);

If you create an ID you will probably never use it since you will query the developer_id and/or project_id in your LEFT JOIN

NOTE: make sure the column definitions are the same as the developer and the project tables.