Logging database changes as far as inserts/deletes/updates, as far as best practices go, is usually done by a trigger on the main table writing entries into a audit table (one audit table per real table, with identical columsn + when/what/who columns). The list of events as a generic list doesn’t exist. It’s really a function … Read more
Turns out you can create a multi-column unique index on an MS access database, but it’s a little crazy if you want to do this via the GUI. There’s also a limitation; you can only use 10 columns per index. Anyway, here’s how you create a multi-column unique index on an MS access database. Open … Read more
This is called the Observation Pattern. Three objects, for the example Book Title=”Gone with the Wind” Author=”Margaret Mitchell” ISBN = ‘978-1416548898’ Cat Name=”Phoebe” Color=”Gray” TailLength = 9 ‘inch’ Beer Bottle Volume = 500 ‘ml’ Color=”Green” This is how tables may look like: Entity EntityID Name Description 1 ‘Book’ ‘To read’ 2 ‘Cat’ ‘Fury cat’ 3 … Read more
The difference between 3NF and BCNF is subtle. 3NF Definition A relation is in 3NF if it is in 2NF and no non-prime attribute transitively depends on the primary key. In other words, a relation R is in 3NF if for each functional dependency X ⟶ A in R, at least one of the following … Read more
I’ve also been looking for a single-page “quick reference” PDF for ERD relationship symbols (i.e. “Crows Feet”). I haven’t found anything I’ve liked, so I created this. I’ve posted the Full Page, Printable PDF on my blog. Hope this helps!
Wow I just wrote a big post and SO choked and hung on it, and when I hit my back button to resubmit, the markup editor was empty. aaargh. So here I go again… Regarding Stack Overflow, it turns out that they use SQL server 2005 full text search. Regarding the OS projects recommended by … Read more
UserRelationship ==== RelatingUserID RelatedUserID Type[friend, block, etc] Agree that mutuality doesn’t belong as a column; breaks normalization.
This is a little bit dated question, but for completeness. What about PgModeler? According to their github repo it’s under GPL3. Schema creation works well.
This is a little bit dated question, but for completeness. What about PgModeler? According to their github repo it’s under GPL3. Schema creation works well.
A star schema really lies at the intersection of the relational model of data and the dimensional model of data. It’s really a way of starting with a dimensional model, and mapping it into SQL tables that somewhat resemble the SQL tables you get if you start from a relational model. I say somewhat resemble … Read more