Hello all,

Just started learning SQL recently.

But one thing i'm still not clear on is alter tables relationships after they've been created.

Instead of creating a foreign key when the table is first created - i create the table and then run a query to set the foreign key and relationship (one-to-one, one-to-many etc)

Anyways, long story short is i want to create a one-to-one relationship with a table but am having problems with adding more than one constraint at a time when altering a table.

Understand yet? Easiest thing to do is show you:

I have 2 tables: Branch_Table and Employee_Table

I want to create a one-to-one relationship between emp_id on the Branch_Table and manager_id on the Employee_Table.

The SQL i've written which doesn't seem to work is:

ALTER TABLE Branch_Table
Add Constraint Branch_Table_FK1 FOREIGN KEY (manager_id)
Add Constraint Branch_Table_UQ1 Unique (manager_id)
References Employee_Table (emp_id));

Am having trouble with that second Add constraint (UQ1 unique). I know it's something to do with the Add syntax above.

So basically, my question is can i create a one-to-one relationship with just the one SQL Query? And how would i do it?

Many thanks in advance.

This syntax may vary between DBMSs, but this works in Oracle:
(You had the REFERENCES clause on the wrong constraint, by the way).