ORM is an anti-pattern | Seldo.Com Blog. I tweeted about ORM last week, and since then several people have asked me to clarify what I meant. I have actually previously written about ORM, but it was in the context of a larger discussion about SQL and I shouldn't have confused the two issues. So here I'm going to focus on ORM itself. I'm also going to try to be very brief, since it became very apparent from my SQL article that people tend to stop reading at the first sentence that makes them angry (and then leave a comment about it, whether or not their point is addressed later on). What's an anti-pattern? I was pleased to discover that Wikipedia has a comprehensive list of anti-patterns, both from within the world of programming and outside of it.
It initially appears to be beneficial, but in the long term has more bad consequences than good ones An alternative solution exists that is proven and repeatable What do you mean by ORM? The benefits of ORM Simplicity: some ORM layers will tell you that they "eliminate the need for SQL". Graph Database Use Cases. Last week we spoke about domain modeling with Neo4j and Django. Today I offer a presentation from Peter Neubauer, COO of Neo Technologies, discussing various use cases that are well suited for graph databases. Couple of quick points with respect to graph databases: Graphs are made up of both nodes and relationships between nodes, another was to say this is vertices and edgesExtension to a regular graph is a property graph, in which, both the nodes and the relationships can both have properties associated with themOne of the key benefits to using graph databases, or at least in Neo4j's case, is the fast traversal between nodes, there is a huge performance gain, especially when compared to a relational database like MySQL.
Peter, provides numerous examples of problems which are nicely handled by graph databases. I'm going to list them with the slide number so you can view the respective slides. [QT][QtSql] Connexion à une BDD microsoft Access. L'accès aux données avec Qt. Beaucoup de frameworks proposent une couche d'accès aux données, c'est-à-dire un système apportant bien souvent une certaine transparence vis-à-vis du SGBD.
Nous n'avons plus à nous préoccuper du driver au niveau du code, puisque ce sera le rôle du framework. Qt en fait partie et nous allons voir quelques-unes des très nombreuses possibilités qu'il offre. Bien évidement, il existe d'autres frameworks, comme .Net par exemple, qui propose son célèbre ADO, mais nous utiliserons Qt pour sa facilité d'utilisation et sa portabilité. Le langage utilisé sera C++ et nous choisirons comme SGBD SQL-Server. Afin de pouvoir suivre ce tutoriel il sera nécessaire de savoir utiliser Qt (notamment le designer et connaître le rôle du .pro). Vous trouverez toutes les informations utiles dans la rubrique Qt.
II-A. Afin d'y voir clair nous nous servirons un MCD, voici donc l'organisation des données: II-B. Le script SQL de création avec SQL-Server Sélectionnez III-A. III-B. III-C. Application.pro QT += sql. A Simple Guide to Five Normal Forms in Relational Database Theory. William Kent, "A Simple Guide to Five Normal Forms in Relational Database Theory", Communications of the ACM 26(2), Feb. 1983, 120-125.
Also IBM Technical Report TR03.159, Aug. 1981. Also presented at SHARE 62, March 1984, Anaheim, California. Also in A.R. Hurson, L.L. Miller and S.H. Pakzad, Parallel Architectures for Database Systems, IEEE Computer Society Press, 1989. [12 pp] Copyright 1996 by the Association for Computing Machinery, Inc. > 1 INTRODUCTION . . . 2 > 2 FIRST NORMAL FORM . . . 2 > 3 SECOND AND THIRD NORMAL FORMS . . . 2 >> 3.1 Second Normal Form . . . 2 >> 3.2 Third Normal Form . . . 3 >> 3.3 Functional Dependencies . . . 4 > 4 FOURTH AND FIFTH NORMAL FORMS . . . 5 >> 4.1 Fourth Normal Form . . . 6 >>> 4.1.1 Independence . . . 8 >>> 4.1.2 Multivalued Dependencies . . . 9 >> 4.2 Fifth Normal Form . . . 9 > 5 UNAVOIDABLE REDUNDANCIES . . . 12 > 6 INTER-RECORD REDUNDANCY . . . 13 > 7 CONCLUSION . . . 13 > 8 ACKNOWLEDGMENT . . . 14 > 9 REFERENCES . . . 14 (c) Unrestricted: