INSERT in a ONE to ONE Relationship
Here again my comment as an answer
since you have a reference in tableB and tableC to tableA, you have to insert tableA first and retreive the generated PK. Then you can insert in any of the other tables with the retrieved ID. For JPA have a look here: How to get Id of last persisted entity using JPA
And here is an example how to achieve this in sql server:http://sqlfiddle.com/#!3/a3f62/3
this is a basic in relational databases and foreign keys, i didnt read the wiki article, but it have to mention same the thinkg: http://en.wikipedia.org/wiki/Foreign_key