Introduction to SQL


What is SQL?
SQL is a Standard—BUT....
SQL is an ANSI standard computer language for accessing and manipulating database systems. SQL statements are used to retrieve and update data in a database. SQL works with database programs like Access, DB2, Informix, SQL Server, Oracle, Sybase, etc. Unfortunately, there are many different versions of the SQL language, but to be in compliance with the ANSI standard, they must support the same major keywords in a similar manner (such as SELECT, UPDATE, DELETE, INSERT, WHERE, and others).

SQL Database Tables
A database most often contains one or more tables. Each table is identified by a name (e.g., “Customers” or “Orders”). Tables contain records (rows) with data. Below is an example of a table called Persons:

LastName FirstName Address City
Hansen Ola Timoteivn 10 Sandnes
Svendson Tove Borgvn 23 Sandnes
Pettersen Kari Storgt 20 Stavanger

The table above contains three records (one for each person) and four columns (LastName, FirstName, Address, and City).