MySQL Create

Create a Database

The CREATE DATABASE statement is used to create a database in MySQL. A database holds one or multiple tables.

Syntax

CREATE DATABASE database_name

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

In the following example we create a database called "my_db":

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con) 

  {

  die('Could not connect: ' . mysql_error());

  }

  if (mysql_query("CREATE DATABASE my_db",$con))

  {

  echo "Database created";

  }

else

  {

  echo "Error creating database: " . mysql_error();

  }

mysql_close($con);

?> 

Create a Table

The CREATE TABLE statement is used to create a database table in MySQL.

Syntax

CREATE TABLE table_name(column_name1 data_type,column_name2 data_type, column_name3 data_type,.......)

We must add the CREATE TABLE statement to the mysql_query() function to execute the command.

Example

The following example shows how you can create a table named "Person", with three columns. The column names will be "FirstName", "LastName" and "Age":

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

  // Create database

if (mysql_query("CREATE DATABASE my_db",$con))

  {

  echo "Database created";

  }

else

  {

  echo "Error creating database: " . mysql_error();

  }

  // Create table in my_db database

mysql_select_db("my_db", $con);

$sql = "CREATE TABLE Person (FirstName varchar(15),LastName varchar(15),
Age int)";

mysql_query($sql,$con);mysql_close($con);

?> 

Important: A database must be selected before a table can be created. The database is selected with the mysql_select_db() function.

Note: When you create a database field of type varchar, you must specify the maximum length of the field, e.g. varchar(15).

MySQL Data Types

Below is the different MySQL data types that can be used:

Numeric Data Types Description

int(size)

smallint(size)

tinyint(size)

mediumint(size)

bigint(size) : Hold integers only. The maximum number of digits can be specified in the size parameter.

decimal(size,d)

double(size,d)

float(size,d) : Hold numbers with fractions. The maximum number of digits can be specified in the size parameter. The maximum number of digits to the right of the decimal is specified in the d parameter.

Textual Data Types Description

char(size) : Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis.

varchar(size) : Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis.

tinytext : Holds a variable string with a maximum length of 255 characters text.

blob : Holds a variable string with a maximum length of 65535 characters mediumtext.

mediumblob : Holds a variable string with a maximum length of 16777215 characters longtext.

longblob : Holds a variable string with a maximum length of 4294967295 characters.

Date Data Types Description

date(yyyy-mm-dd)

datetime(yyyy-mm-dd hh:mm:ss)

timestamp(yyyymmddhhmmss)

time(hh:mm:ss) : Holds date and/or time

Misc. Data Types Description

enum(value1,value2,etc) : ENUM is short for ENUMERATED list. Can store one of up to 65535 values listed within the ( ) brackets. If a value is inserted that is not in the list, a blank value will be inserted.

SET is similar to ENUM. However, SET can have up to 64 list items and can store more than one choice.

Primary Keys and Auto Increment Fields

A primary key is used to uniquely identify the rows in a table. Each primary key value must be unique within the table. Furthermore, the primary key field cannot be null because the database engine requires a value to locate the record. Each table should have a primary key field.

The primary key field is always indexed. There is no exception to this rule! You must index the primary key field so the database engine can quickly locate rows based on the key's value.

The following example sets the personID field as the primary key field. The primary key field is often an ID number, and is often used with the AUTO_INCREMENT setting. AUTO_INCREMENT automatically increases the value of the field by 1 each time a new record is added. To ensure that the primary key field cannot be null, we must add the NOT NULL setting to the field.

Example

$sql = "CREATE TABLE Person(personID int NOT NULL AUTO_INCREMENT, 
PRIMARY KEY(personID),FirstName varchar(15),LastName varchar(15),Age int)";
 mysql_query($sql,$con);