VB.NET OleDb access database entry rule to link 3 fields as unique

Question

I'm not certain how to title this question, but here's my question. I'm new to Databasing so this might be simple, but no one I've asked has a clue how to do it.

Is there a rule I can write in an access database that will link 3 entries to equal one unique value?

CREATE TABLE x(
_a_ int,
_b_ varchar(255),
_y_ int,
_z_ varchar(255)
); 

i.e. the above table, I wish a, b, and y to be unique when looked at together, but each individual entry can be set non-uniquely. How would I go about linking tables with a rule like this when only one entry is present, or should I rewrite the tables to reflect this change?

I'm writing this code in VB.NET to access the database, I'm editing the database using access, and I have VS2012. I've been using OleDb to access the DB, but I suppose that's all mostly irrelavent since I'm asking about the database settings and SQL statements/rules as opposed to the programming.

Answer 1

Try adding a CONSTRAINT:

CREATE TABLE x(
  _a_ int,
  _b_ varchar(255),
  _y_ int,
  _z_ varchar(255),
CONSTRAINT pk_Keys PRIMARY KEY (_a_, _b_, _y_)
);