Posted by Michael Satterwhite on 11/23/85 11:16

tony yau wrote:
| Hi All
|
| Thanks for all your comments on my previous mail, very much
appreciated.
| I'm stuck again!
| I've created the following lookup table for m <-> m relationship
between
| a Group and a Contact table.
|
| CREATE TABLE Group_Contact(
| GroupID INT NOT NULL,
| ContactID INT NOT NULL,
|
| Index (GroupID),
| FOREIGN KEY (GroupID) REFERENCES Group (PKey) ON DELETE CASCADE,
| Index (ContactID),
| FOREIGN KEY (ContactID) REFERENCES Contact (PKey) ON DELETE CASCADE
| ) TYPE=InnoDB COMMENT='Group to Contact lookup';
|
| what do I need to do to ensure only unique (GroupID,ContactID) pair can be
| inserted into the table?

This question is really a MySQL question. You might want to join their
mailing list as you'll get better answers for this type of question there.

That said: The easiest way would be to make GroupId, ContactID a unique
index. In this case, primary key would be OK. Add the statement

Primary Key(GroupID, ContactId),

just before the first "Index" statement.

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