Understanding Databases |
Each column represents an attribute or property of that specific object. This could be the number of legs that a creature has; the type of vehicle, model number of a vehicle or a book's ISBN. The idea with columns is that it should never include more than one attribute, in other words each column must describe one and only one attribute of a specific object. Each column in a row has a data type. This data type defines the type of information or data that can be stored in such a cell. Among these data types are: The designer of a database can specify whether a column can be empty or by some means force for a value to be entered. A primary key of a table uniquely identifies each object. In other words, there can never be two objects that are the same or have the same primary key. To make it easier for users, most database developers prefer system generated primary key. This also means that a primary key column can not have a null value (being empty). As you experiment with different relational database systems such as Oracle, Access, MSSQL server, Sybase, MySQL and so forth, you will notice that the syntax used by each system is slightly different from the other, but the database fundamentals discussed here are the same across the board. You will also find many tools that are used to design databases, but most advanced developers prefer using a language called Transact-SQL to create database and its tables. |
RELATED ARTICLES:
Creating database tables with SQL
To create a table in SQL, you use a command that requires the name of the table as well as names and data types of the fields of that table. In general, the syntax for creating a table is as follows: CREATE table_name ( column_name data_type); The table nam
Database Design
After gathering and analyzing your requirements, and depending on whether or not your application needs a database to store information; database design is the next big thing. This comes even before you start coding the application program. The reason for this is that, the application program
Database schemas, domains and constraints
There is more to a database than just a collection of tables. In addition to tables, there are structural aspects that maintain the integrity of data stored in databases. This tutorial will cover the structural aspect of any relational database. These include schemas, domains and constraints.
Creating and dropping SQL Views
In SQL, a view is like a virtual table. It be haves like a table except it does not store any data. Meaningful use of a view is usually to gather and simplify presentation of data from multiple tables. A view is compiled once and is stored on the database server and can be used wh
Selecting data from multiple tables
So far we have covered methods of retrieving data from single table. In real life however, you hardly get to only retrieve data from one table. In other words, to retrieve and interpret information, you normally get such information from different tables each of which will contain only information a
Understanding Numbers
In mathematics understanding the type of numbers you are working with is very important. That understanding influences how you perform arithmetic or deal with those numbers under different circumstances. This posting will explore the type of numbers that are common
Creating your business web site
There are thousands of business websites on the World Wide Web. These websites serves as a means to inform your customers, suppliers, media contacts and other interested parties about your business and its offerings. Thus it is important to deliver essential information in a wa
Understanding Internet Marketing
Anyone who does business on the internet or thinking of doing so must think about internet marketing. Internet marketing is a way of getting and giving attention from and to potential customers. Internet marketing involves using t
Common SQL Data types
Now that you have identified your data entities or tables, you have to define each attribute of the tables you have identified. These definitions include the name of the attribute and the type of data that can be stored in the field. Most relational database systems have a number of data types that
The state of Periodic table elements
- In addition to the group 8 or O elements, the following elements also naturally occur in gas state: H, N, O, F, Cl and Br -Among metals and non-metals, the following occurs in liquid state: Na, K, Rb, Cs, Fr, Hg a