MySQL几个注意点

1、在创建表、对表进行操作之前，必须首先选择数据库。通过 mysql_select_db() 函数选取数据库。当您创建 varchar 类型的数据库字段时，必须规定该字段的最大长度，例如：varchar(15)。

 <?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);
 $sql = "CREATE TABLE Persons
 (
 FirstName varchar(15),
 LastName varchar(15),
 Age int
 )";
 mysql_query($sql,$con);

 mysql_close($con);
 ?>

2、mysql_fetch_array() 函数以数组的形式从记录集返回第一行。每个随后对 mysql_fetch_array() 函数的调用都会返回记录集中的下一行。

<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons");

while($row = mysql_fetch_array($result))
  {
  echo $row['FirstName'] . " " . $row['LastName'];
  echo "<br />";
  }

mysql_close($con);
?>

将查询结果显示在表格中。

<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons");

echo "<table border='1'>
<tr>
<th>Firstname</th>
<th>Lastname</th>
</tr>";

while($row = mysql_fetch_array($result))
  {
  echo "<tr>";
  echo "<td>" . $row['FirstName'] . "</td>";
  echo "<td>" . $row['LastName'] . "</td>";
  echo "</tr>";
  }
echo "</table>";

mysql_close($con);
?>

3、