SQL

SQL (Structured Query Language) is a standard interactive and programming language for getting information from and updating a database. Although SQL is both an ANSI and an ISO standard, many database products support SQL with proprietary extensions to the standard language. Queries take the form of a command language that lets you select, insert, update, find out the location of data, and so forth. There is also a programming interface

Restore Point

A restore point is a saved "snapshot" of a computer's data at a specific time. Restore points are a component of the Windows System Restore utility. By creating a restore point, you can save the state of the operating system and your own data so that if future changes cause a problem, you can restore the system and your data to the way it was before the changes were made. When a restore point is established, your computer creates a backup copy of all data at that particular time.

DKNF

Domain/key normal form (DKNF). A key uniquely identifies each row in a table. A domain is the set of permissible values for an attribute. By enforcing key and domain restrictions, the database is assured of being freed from modification anomalies. DKNF is the normalization level that most designers aim to achieve.

3NF

Third normal form (3NF)- At the second normal form, modifications are still possible because a change to one row in a table may affect data that refers to this information from another table. For example, using the customer table just cited, removing a row describing a customer purchase (because of a return perhaps) will also remove the fact that the product has a certain price. In the third normal form, these tables would be divided into two tables so that product pricing would be tracked separately.

2NF

Second normal form (2NF). At this level of normalization, each column in a table that is not a determiner of the contents of another column must itself be a function of the other columns in the table. For example, in a table with three columns containing customer ID, product sold, and price of the product when sold, the price would be a function of the customer ID (entitled to a discount) and the specific product.

1NF

First normal form (1NF). This is the "basic" level of normalization and generally corresponds to the definition of any database, namely:

* It contains two-dimensional tables with rows and columns.
* Each column corresponds to a sub-object or an attribute of the object represented by the entire table.
* Each row represents a unique instance of that sub-object or attribute and must be different in some way from any other row (that is, no duplicate rows are possible).
* All entries in any column must be of the same kind. For example, in the column labeled "Customer," only customer names or numbers are permitted.

Normalization

In creating a database, normalization is the process of organizing it into tables in such a way that the results of using the database are always unambiguous and as intended. Normalization may have the effect of duplicating data within the database and often results in the creation of additional tables.

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.