I�m using Oracle 10g and trying to set an 1-to-many (1�m) constraint between two tables. The �many� means 1, 2, 3, � etc., not including 0. I know how to set foreign key constraint, but not this type of 1-to-many (1, 2, 3, �) relation. Can anyone help?
How would you insert a record in the parent table with this constraint? - You can't enter a child record, because it violates the foreign key rule (the parent record does not exist). - You can't enter a parent record, because you only allow parents with at least one child.
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Is it possible to create an entry in the parent table first and then an entry in child table in the same transaction, and then commit?
I'm asking this question b/c many data modeling tools do support this type of 1-to-many (1,2,3...M) relation.
You cannot enter a foreign key if there is no entry in the "parent" table corresponding. You cannot enter in the "parent" table if you insist on there being a "child" first. You have set yourself an impossible task.
For a very short time, after entering your "parent" table line and before entering your "child" table line, you are going to have to live with a 0..* (zero-to-many) relation.