So what are the advantages in using Django? It does make the modelling easy, but it also adds some extra constraints or complexities. There are many advocates of Django and many places where people will try to answer the question “Why use Django?” In the table below, I have included links to eight such articles, [...]
Some time ago when we looked at modelling the simple example of Hezekiah’s tunnel (EPANET Network Components – Database tables and rows, Part 1 (#18)), we discussed the options for creating our data tables including some ways to use a class hierarchy. EPANET has nodes (junctions, reservoirs and tanks) and links (pipes, pumps and valves) which [...]
Different applications have different requirements. This seems to be an obvious statement, but sometimes it is not obvious just how different the requirements can be. […]
Many software programs that model water supply networks use the public domain EPANET modelling engine for analysis. EPANET defines many different types of object which can be contained in such networks and settings for simulation of events in the networks. EPANET also defines an input file format which can describe these objects and settings. [...]
In this post we are trying to come to some conclusions about the different sub-classing options in Django that have been discussed in previous newsletters. Due to the long delay between posts, I have listed the options again below as a reminder. […]
In this post we are looking at the basic performance of the different sub-classing options in Django that have been discussed in previous posts. The three options are listed again below. […]
When modelling data, we often need to distinguish between different types of objects. For example, a mapping application may need to store information about both roads and lakes, or a library catalogue may need to store data about both books and DVDs. With these examples, the objects can be quite diverse and the details stored [...]
Data modelling is not the only limiter of performance. When I first started working with databases, performance in all aspects of computing was much worse than it is now. However well an expert might craft a query, and however simple the query might be, technical restrictions would always limit the performance to just a few [...]
A very common problem with databases is missing data. Missing data makes searches difficult (or impossible) and statistics unreliable. Two common reasons for this are: Records contain optional fields which have been left empty. Records are completely missing because some of the mandatory information was not available. Since the missing data was in mandatory columns, [...]
In this series of newsletters, we concentrate on data modelling in general and discuss relational databases when we need to consider specific applications. In general, we do not consider the so-called “NoSQL” databases. Relational database management systems lend themselves to the use of fixed schemas and also provide easy type checking. […]