Normalization

Normalization is a technique for designing relational database tables to minimize duplication of information and, to safeguard the database against certain types of logical or structural problems, namely data anomalies.
Normalization is typically a refinement process after the initial exercise of identifying the data objects that should be in the database, identifying their relationships, and defining the tables required and the columns within each table.
For example, when multiple instances of a given piece of information occur in a table, the possibility exists that these instances will not be kept consistent when the data within the table is updated, leading to a loss of data integrity. A table that is sufficiently normalized is less vulnerable to problems of this kind, because its structure reflects the basic assumptions for when multiple instances of the same information should be represented by a single instance only.
Higher degrees of normalization typically involve more tables and create the need for a larger number of joins, which can reduce performance.

There are two goals of the normalization process:
a. Eliminating redundant data (for example, storing the same data in more than one table) and
b. Ensuring data dependencies make sense (only storing related data in a table).

Both of these are worthy goals as they reduce the amount of space a database consumes and ensure that data is logically stored.