Oracle MySql

MYSQL

What Is a Database?

A database is a collection of data. Databases implemented through a computer are created within software. That software, commonly known as a database application, controls how. RDBMS, which is an acronym for relational database management system. Database servers usually have one or more distinct APIs for programmatically creating, accessing,

Managing, searching, and replicating the data they hold. It is through the API that you connect to and work with data stored in database servers when using PHP. There is no requirement that an RDBMS be used to store data. Other data stores can be used such as a flat file or a table known as a hash table. These are perfectly fine for some applications, especially smaller applications; however, for larger applications or applications that require optimal speed for large data stores, an RDBMS is a requirement.

PHP-Supported Databases

PHP Data Objects (PDO) was introduced back with the 5.1 release of PHP. PDO creates a consistent, abstracted interface to database servers and data. PHP offers several database-specific drivers for both PDO and non-PDO access. The PHP web site contains a list with the latest information about databases that can be integrated along with the PDO abstraction layer and other abstraction layers. MySQL, is an incredibly popular and powerful RDBMS. MySQL provides one of the letters in the ubiquitous  كل الوجودacronym اللفظة الاوائلية“LAMP,” which is an abbreviation for Linux, Apache, MySQL, PHP/Perl/Python. MySQL has become so popular for several reasons. 1- MySQL is free, 2- MySQL is also stable, meaning that it’s not prone عرضةto crashing even under load.3- MySQL is lightweight, meaning that it doesn’t require many resources to install or run.4- MySQL is fast and easy to use. 5-MySQL is powerful, with all of the features required for web applications. MySQL AB, which is the company behind MySQL (owned by Sun), changed the licensing for MySQL relatively recently. In the latest iteration as of this writing, MySQL offers a product called MySQL Server Community Edition, which is essentially the same as the MySQL Enterprise Server, but is lacking official MySQL support and some graphical user interface (GUI) tools. If your organization needs an officially supported product, where you can call for assistance with the database server at any time, then MySQL Enterprise is for you. MySQL AB’s support is excellent; it’s not unheard of to get responses from developers themselves. Otherwise, the MySQL Server Community Edition is your choice. I’ll be concentrating on the MySQL Server Community Edition in this book.

Summary

The great advantage of the Web is its capability to make large quantities of information publicly

available quickly and cheaply. This functionality has been tremendously بشكل مروع enhanced by the recent

increase in availability of inexpensive, reliable databases. PHP supports several types of databases, including flat-file, hash, and relational databases. Most

large web sites (and even small sites, too) use some sort of relational database management system

(RDBMS). MySQL is a common choice among PHP developers. MySQL is not only free but also lightweight, stable, and full of features necessary for both online and offline applications.

Relational Databases and SQL

SQL is the language of relational databases. A simple query like a one-table SELECT will be more or less the same whether you’re using a tiny database like mSQL or an expensive like Oracle. The big advantage for you, the web developer, is that, after you learn SQL, you will be able to interact with numerous databases across all platforms without a steep retraining curve. Just imagine how horrible life would be if Oracle, MySQL, and SQL Server all had entirely different sets of commands

for putting data in and getting data out of their stores — as if Oracle used SELECT to ask for data sets, MySQL used VALJ (the developers are Swedish, you know), and SQL Server used FIND IT IN THIS TABLE (to better match the vocabulary of Windows). SQL is the common vocabulary and syntax that will save you from this nightmare. There are differences among products, and in their implementations of the SQL standard and the extensions they each define to that standard, but it’s better to have 80 percent in common and 20 percent different than the other way around.

The Workhorses of SQL

data manipulation statements are supported by every SQL server and will constitute an

extremely high percentage of all the things you’ll want to do with a relational database. These four

horsemen of the database are SELECT, INSERT, UPDATE, and DELETE. These commands are your friends and helpmates; get comfy with them, and they will serve you well. The thing to remember about these four SQL statements is that they manipulate only database values, not the structure of the database itself. In other words, you can use these commands to add data but not to make a database; you can get rid of every piece of data in a database, but the shell will still be there — so, for instance, you wouldn’t be able to name another database on the same server with the same name. If you want to add or get rid of columns, blow away entire databases as if they never existed, or make up new databases, you need to use other commands such as DROP, ALTER, and CREATE.

SQL queries are usually quite whitespace insensitive

Joins

Joins are one of the main useful features of SQL.

A SELECT statement on a single table without joins might be visualized as being something like a row in a spreadsheet. But an SQL database is by definition relational. To understand the philosophy behind the relational database concept, you have to think back to some occasion on which you were forced to fill out a whole bunch of forms — such as applying for a loan, visiting a doctor’s office for the first time, or dealing with some kind of governmental formality. (If you’ve never had this experience, it’s because you’re young enough to have lived entirely in a world of relational databases.) As you were writing down your name, address, phone, and Social Security number for the 15th time you probably thought, “Why can’t I just write my address down once, and then they could just look it up on a need-to-know basis?” That’s exactly the concept behind a relational database.the way a relational database differs from paper forms is the main identifier. Humans do well with text and prefer to categorize by textual identifiers such as names. If a dentist’s office or auto body shop stored its paper files in numerical order, it would be difficult for anyone to lay his hands on John Johnson’s forms when John next required service. Frankly, most paper file users these days ask for your Social Security number as a backup — it works solely to differentiate you from other people in their files with exactly the same first, last, and middle names. Databases, on the other hand, work well with integers. You’ll frequently use integer values to create unique identifiers or IDs within a database table. This field or column is then called a primary key, which indicates that each value in that column will be unique and that the rows within that column will always have a value in the primary key field. Because primary keys are unique by nature, a database needs only one to identify a person, place, or thing uniquely — no matter how many tables refer to that piece of information. So instead of needing to repeat information several times, like this:Name: John Johnson

SS#: 123-45-6789

Name: John Johnson

Fears: Cats, Friday the 13th, Flying

Name: Jane Jones

SS#: 987-65-4321

Name: Jane Jones

Fears: Heights, Flying

with a relational database you can write down each piece of information just once and then relate it to each other piece using integers, as shown in Tables 13-1 to 13-3.

 

This is clearly a neater and faster (for a database) way to store this information. But when you need

to pull out the data into a human-readable form, there’s a problem: You have to get and correlate

information from more than one database. That’s the job of a join.