Tabel relationer

You need a field which for example is to be your foreign key. This will normally be a long integer.

ALTER TABLE YourTable ADD CONSTRAINT FK_ID FOREIGN KEY (SomeField) REFERENCES SomeOtherTable (SomeOtherField)

FK_ID is the foreigen key field (long integer for example) which is to refernce the primary key field (SomeOtherField) in the related table (SomeOtherTable)

actually you do NOT need to have a foreign key/primary key relationship to make a select on two tables but it helps because they will (should) both be indexed.

sorry! FK_ID is the name of the INDEX which you give to field (SomeField)

jeg laver en tabel med den her SQL sætning

sqlStatement =
    "CREATE TABLE " + hovedmenu + " (t_ID AUTOINCREMENT CONSTRAINT AUTONUMBER PRIMARY KEY, indhold MEMO, undermenuid NUMBER)";

og feltet "undermenuid" skal relateres til et felt der hedder "u_ID" i en tabel der hedder "undermenu"

So you should be able to use something like
ALTER TABLE YourTable ADD CONSTRAINT FK_undermenuid FOREIGN KEY (undermenuid) REFERENCES undermenu (u_ID)

and you need to alter the name of the table YourTable to what ever it is in + hovedmenu +

cool, hvad hvis der skal være "referentiel integritet" og "kaskadevis sletning af relaterede poster"

By adding a primary key/foreign key constraint you have referential integrity. I'm not sure if it is at all possible to add cascade deletes using SQL. This isnt common to all databases so I dont think its standard.

I'll see if I can find something and get back!

ok, thanks alot

Hi c-lund
I dont seem to be able to find anything concering cascade delete in SQL. If you do find anything yourself can you drop a comment please, and I'll do the same.

det skal jeg nok, men jeg kan ikke helt få din sætning til at virke, skal den komme efter det her
sqlStatement =
"CREATE TABLE information(t_ID AUTOINCREMENT CONSTRAINT AUTONUMBER PRIMARY KEY, indhold MEMO, undermenuid NUMBER)";
Connection.Execute(sqlStatement);

men hvordan skal den så se ud???
ALTER TABLE YourTable ADD CONSTRAINT FK_undermenuid FOREIGN KEY (undermenuid) REFERENCES undermenu (u_ID)

You should be able to do both in the same SQL
"CREATE TABLE information(t_ID AUTOINCREMENT CONSTRAINT AUTONUMBER PRIMARY KEY, indhold MEMO, undermenuid NUMBER CONSTRAINT FK_undermenuid REFERENCES undermenu (u_ID))";

You MUST have a table named undermenu with a primary key field named u_ID and it should also be a number field