Wednesday 29 May 2013

MySQL Introduction


MySQL is the most popular open-source database system


What is MySQL?

MySQL is a database.
The data in MySQL is stored in database objects called tables.
A table is a collections of related data entries and it consists of columns and rows.
Databases are useful when storing information categorically. A company may have a database with the following tables: "Employees", "Products", "Customers" and "Orders".


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).



Queries

A query is a question or a request.
With MySQL, we can query a database for specific information and have a recordset returned.
Look at the following query:
SELECT LastName FROM Persons
The query above selects all the data in the "LastName" column from the "Persons" table, and will return a recordset like this:
LastName
Hansen
Svendson
Pettersen

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