A database holds one or multiple tables.
一个数据库包含一张或多张表。

Create a Database
创建一个数据库

The CREATE DATABASE statement is used to create a database in MySQL.
“CREATE DATABASE”语句是用来创建MySQL数据库的。

Syntax
语法

CREATE DATABASE database_name

Example
案例

In the following example we create a database called "my_db":
在下面的案例当中，我们建立了一个名为“my_db”的数据库：

<?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
建立一张表

The CREATE TABLE statement is used to create a database table in MySQL.
“CREATE TABLE”语句使用于在MySQL中建表的指令。

Syntax
语法

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.
我们必须在mysql_query()函数中加入“CREATE TABLE”来执行这个指令。

Example
案例

The following example shows how you can create a table named "Person", with three columns. The column names will be "FirstName", "LastName" and "Age":
通过下面的案例，我们演示了如何创建一个名为“Person”的表；它包含三个列，每个列的名称分别为："FirstName", "LastName" 和 "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.
重点：必须先指定数据库以后，才能够在其中建立表单；数据库通过mysql_select_db()函数来指定。

Note: When you create a database field of type varchar, you must specify the maximum length of the field, e.g. varchar(15).
注意：如果在数据库中需要用到varchar类型的字段，那么你必须指定这个域的最大长度，如：varchar(15)。

MySQL Data Types
MySQL数据类型

Below is the different MySQL data types that can be used:
下面列举了不同的MySQL数据类型：

Primary Keys and Auto Increment Fields
关键字段[Primary Keys Field]和自动增加字段[Auto Increment Field]

Each table should have a primary key field.
每张表都包含一个关键字段。

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.
关键字段是用来确认一张表中记录的唯一性的。一张表中的每个私钥值都必须是独一无二的。而且，私窑不可以是空值（null），因为数据库引擎（database engine）需要一个值对记录进行定位。

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.
关键字段必须被指明，无一例外。你必须指明关键字段使得服务器可以对基于关键字段的记录进行定位。

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.
下面这个案例设置了“personID”作为关键字段。关键字段通常是一个ID，他经常与AUTO_INCREMENT属性一起使用。AUTO_INCREMENT属性会在一条记录被添加后自动将“值”加“1”。为了确保关键字段不是空值，我们必须再加上“NOT NULL”属性。

Example
案例

$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);

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