Author: Agnieszka Kozubek

Chief Scientist at Vertabelo

How to import an existing database into Vertabelo: Reverse Engineering

The newest Vertabelo feature is Reverse Engineering: a way to import an existing database into Vertabelo. The Reverse Engineering tool is a simple command-line Java application that you can download from our website. It connects to your database, reads the table and view details and stores the info in an XML file. Import the XML file into your database model and voila - your database is in Vertabelo! How to use the reverse engineering application Download the Reverse Engineering application from our website, then run the Reverse Engineering application.

Theory and History: Why are Relational Databases “Relational”?

Many people wonder why relational databases are called “relational.” Some think that it’s because of a logical entity-relationship model you often start your design with. Or, because you have tables and relationships (aka foreign keys) between them. But that’s not the case. The name comes from the mathematical notion of “relation.” It all started with E. F. Codd who in 1970 (in the article A Relational Model of Data for Large Shared Data Banks) proposed something now called relational algebra as the mathematical foundation of databases.

Oracle VARCHAR2 Column Size

Recently a fellow database architect claimed that in Oracle the type VARCHAR2(255) means a string of 255 bytes, not characters. There is not much difference between the two in the English-speaking world. It matters though if you want to handle people with names like Kołłątaj. (Not that Hugo Kołłątaj – a famous Polish 18th century politician – would ever use any of our systems, but he became our byword for all non-pure-ASCII names).

Why Doesn’t SQL*Plus Execute My Script?

The question: Why doesn’t my script create tables? The other day I was testing Oracle SQL scripts generated by Vertabelo. Roughly, this is the code that was generated: ... -- Table: book CREATE TABLE book ( id integer NOT NULL, title varchar2(120) NOT NULL, isbn varchar2(15) NOT NULL, PRIMARY KEY (id) ) ; ... I used sqlplus to execute my script and see if it’s correct. sqlplus (database-details) The script run without errors but the tables where NOT created.