Foreign Key

Relational Database 101 {2}

by Kathy S
For those students who have no prior experience or knowledge of database design, this is a great read for you. The author of the article explains the introductory terms and information about how data is organized and represented in a Relational Database. The following are the basics one needs to know. In a relational database, data is stored in a two-dimensional matrix (table) and within the table there are multiple columns and rows. Relational Database Management System (RDBMS) software is used to give ability to users to read and manipulate data. The RDBMS relies on SQL (Structured Query Language) constructs and keywords to access the tables and data that is contained within the tables’ columns and rows. It clarifies that each table in a relational database contains information about a single type of data and has a unique name that is distinct from all other tables in that schema (a grouping of objects/tables that serve a similar business function). The author points out the key to good relations. The primary key is very important; it is a column that ensures uniqueness for every row in a table. The author then explains how a relational database connects (relates) tables and organizes information across multiple tables. The foreign key is an important connector that identifies a column or set of columns in one table that refers to a column or set of columns in another table. The author then states that the key to understanding relational databases is knowledge of data normalization and table relationships. The objective of normalization is to eliminate redundancy and thereby avoid future problems with data manipulation. There are 5 most commonly accepted normal forms, but many programmers, analysts, and designers do not normalize beyond the 3rd normal form,  although experienced database designers may. The author goes on to talk about what 1st, 2nd, and 3rd normal forms look like. Lastly, the article mentions how SQL fits in. SQL helps to create new data, delete old data, modify existing data, and retrieve data from a relational database. read more...

Database Design Mistakes {3}

by Hieu H
A poorly designed database can lead to many problems down the road. It may not be apparent at first, since there is very little data, but as the database grows, you may start to experience inefficiencies and poor performance. Some of the seven most common mistakes that database professionals make include not spending enough (or any) time on documentation, little or no normalization, building before designing, improper storage of reference data, not using foreign keys or constraints, not using naming standards, and improperly choosing primary keys. read more...