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SQL Primer


SQL - Structured Query Language

SQL is the standard language for accessing and manipulating databases.

Common database management systems are: MySQL, SQL Server, Access, Oracle, Sybase, and DB2

Knowledge of SQL is invaluable for anyone who wants to store or retrieve data from a database.


What is SQL?

  • SQL stands for Structured Query Language
  • SQL allows you to access a database
  • SQL is an ANSI standard computer language
  • SQL can execute queries against a database
  • SQL can retrieve data from a database
  • SQL can insert new records in a database
  • SQL can delete records from a database
  • SQL can update records in a database
  • SQL is easy to learn

SQL Database Tables

A database usually 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).


SQL Queries

With SQL, we can query a database and have a result set returned.

A query like this:

SELECT LastName FROM Persons

Gives a result set like this:

LastName
Hansen
Svendson
Pettersen


How to Learn SQL?

Study our Complete SQL tutorial



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