SQL Data Types Overview In SQL as in many other programming languages every piece of data has a particular type. For example 11 is an integer and Wall Street” is a text string. The SQL standard defines many data types to accommodate almost any type of data. Some cases arise where the SQL standard does not adequately support certain...
Procedural languages provide the fundamental method for programming within an SQL database. In other articles in this series we have covered the SQL-based procedural languages but those are generally not the only procedural languages found in an SQL database. Procedural extensions for Perl and Java tend to be the most popular additions but some database...
SQL Programming Overview In the article SQL Programming we discussed creating the Hello World function in PostgreSQL MySQL and Oracle. In this article we take Hello World one step farther and introduce the parts of a function and how to pass parameters to a function. This article uses PostgreSQL’ s PL pgSQL...
SQL Programming Overview Anybody who has done something for a long time has probably wanted to change how things work at some point or another. A worker at a mill might have found a more efficient way of cutting logs or a mathematics teacher might have had a hand in changing a school’ s algebra curriculum. SQL lets you change how things work...
Distributed Databases Overview Suppose you created a database for a web application a few years ago. It started with a handful of users but steadily grew and now its growth is far outpacing the server’ s relatively limited resources. You could upgrade the server but that would only stem the effects of the growth for a year or two. Also now...
Database Concurrency and Reliability Overview Concurrency and reliability have long been hot topics” of discussion among developers and users of distributed systems. The fundamental problem can be seen in a simple example as follows. Suppose two users are working on the same part of a database at the same time. They both UPDATE the...
What is a Relational Database Popular modern databases are built on top of an idea called relational algebra” which defines how relations” e.g. tables and sequences in databases interact within the entire set” of relations. This set of relations includes all the relations in a single database. Knowing...
SQL Keys Overview In SQL keys are used to maintain referential integrity among relations. Put simply this means keys allow tables to reference each other and each reference will be correct” every time. Referential integrity also prevents records from being dangled” or orphaned” by another record that has been...
SQL Table Commands Overview As mentioned previously in this series of SQL articles databases are primarily composed of tables. The columns and rows” structure of the table allows data to be efficiently inserted manipulated updated and deleted from the database. The three most important commands used to work with tables CREATE TABLE...
SQL Overview The SELECT command in SQL provides a robust means for retrieving data from a database. More specifically SELECT returns a result set of zero or more rows from the database and this result set corresponds to the query that was executed. The result set is calculated by the query optimizer inside the database system based on the information...
Database Overview You have been using databases for a few years and you think you are at the top of your game. Or perhaps you have been interested in databases for a while and you think you did like to pursue a career using them but you do not know where to start. What is the next step in terms of finding more rewarding education and employment There...
Database Interaction Efficient interaction efficient storage and efficient processing are the three key properties of a successful database platform. In this article we explore the first efficient interaction. Interaction Category 1 Command Line Clients Many database platforms are shipped with a simple command line utility that allows the user...
Like any technology that strives to be interoperable among different implementations SQL has been standardized. The first SQL standard was adopted and published by the American National Standards Institute ANSI in 1986. The standard was further ratified by the International Organization for Standardization ISO in 1987 and ISO continues to be the...
The Structured Query Language SQL is the computer language in which a user or an application communicates with an SQL-capable database system. SQL database systems include PostgreSQL MySQL Oracle and many others in popular use. The language is standardized by the American National Standards Institute ANSI and the International Organization...
Early Databases In the 1960s the System Development Corporation one of the world’ s first computer software companies and a significant military technology contractor first used the term data base” to describe a system to manage United States Air Force personnel. The term databank” had also been used in the 1960s to...
When you are in a big electronics store buying the latest edition of the iPod how does that store’ s inventory tracking system know you just bought an iPod and not for example a car stereo or a television Let’ s walk through the process of buying an iPod and consider all the implications this has on the inventory database that sits...
Have you ever wondered the name of a movie you watched years ago and although it was on the tip of your tongue the few words of that short title just wouldn’ t come out What about a book you read when you were younger that had a particularly compelling story to tell and despite every effort on your part to relate that story to a friend the...
A view is nothing but a window of an existing table by which one can view and can also change the values in tables. The main point aspect of view is views have no storage space. For this reason views are also called as virtual tables. Thus in other words a view is a database object that gives a logical representation of one or more database tables. As...
The Evolution of Database systems File Management System Hierarchical database System  Network Database System  Relational Database System File Management System The file management system also called as FMS in short is one in which all data is stored on a single large file. The main disadvantage in this system...
COUNT is a group function returns  result by summarizing multiple rows. All group by value function will have the usage of DISTINCT or ALL option and so is the COUNT which uses the DISTINCT option. DISTINCT option is used to enforce uniqueness and  if combined with COUNT is used to count only unique mentioned value. To understand this let...