如何在SQL中引用多个外键到一个表

Question

I want to create a data warehouse and I decided to use some field in more than one table to increase the speed!

But I have a problem: How can I reference more than one foreign key to one table in SQL?

For example: if I have a table for calendar like this:

calendar(c_id, year, month, day)

and another table for daily snapshots like this:

snapshot(id, c_id, year, ...) 

How can I reference both 'c_id' and 'year' from snapshot to calendar table?

Thank you.

Answer 1

Try something like this:

ALTER TABLE calendar ADD CONSTRAINT UQ_calendar_c_id_year UNIQUE (c_id, year)

ALTER TABLE snapshot ADD CONSTRAINT FK_snapshot_c_id_year 
    FOREIGN KEY (c_id, year) REFERENCES calendar (c_id, YEAR)