3
votes
2answers
107 views

Finding violations of the symmetry constraint

Suppose I have a table Friends with columns Friend1ID, Friend2ID. I chose to represent each friendship with two records, say (John, Jeff) and (Jeff, John). Thus, each pair of friends should show up ...
2
votes
2answers
468 views

How to select a subset of data from a large ER model?

I have a quite large ER model in my database and lots of data. Now I would like to take a subset of this data into a different database for testing purposes. The problem is how to get a subset from ...