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)。

 1 <?php

 2 $con = mysql_connect("localhost","peter","abc123");

 3 if (!$con)

 4   {

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

 6   }

 7 

 8 // Create database

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

10   {

11   echo "Database created";

12   }

13 else

14   {

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

16   }

17 

18 // Create table in my_db database

19 mysql_select_db("my_db", $con);

20 $sql = "CREATE TABLE Persons 

21 (

22 FirstName varchar(15),

23 LastName varchar(15),

24 Age int

25 )";

26 mysql_query($sql,$con);

27 

28 mysql_close($con);

29 ?>

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、