Kolonneorientert databasesystem
Computerworld har et whitepaper om kolonneorientert databasesystem. De mener denne databasen kan være en løsning på det enormt økende lagringsbehovet for statistikkgrunnlag.
Predicates in Core Data
Database programming is all about filtering and sorting tables linked to each other. According to the book Core Data , «Core Data is Apple’s object graph management and persistency framework for iOS, OS X, watchOS, and tvOS.» In a sense, predicates are an object version of the WHERE clause in SQL. Just like NSFetchRequest represent the FROM clause in SQL. I never have had problems with WHERE and FROM in SQL, but the predicate format strings in Core Data has been quite a struggle for me. I don’t think the struggle is only my fault. Predicates should clearly be thought, at least to me, as a method of writing WHERE clauses. Here is some notes from tutplus’ Core Data and Swift: Relationships and More Fetching : let predicate = NSPredicate(format: "%K == %@", "last", "Doe") The predicate format string uses %K (K stands for Key) for the property name and %@ for the value. let predicate = NSPredicate(format: "%K >= %i", ...
