详解MySQL插入和查询数据的相关命令及语句使用

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详解MySQL插入和查询数据的相关命令及语句使用_MySQL

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May 30, 2016 pm 05:10 PM

mmysqlOrderInsert dataQuery data

插入数据
MySQL 表中使用 INSERT INTO SQL语句来插入数据。
你可以通过 mysql> 命令提示窗口中向数据表中插入数据，或者通过PHP脚本来插入数据。
语法
以下为向MySQL数据表插入数据通用的 INSERT INTO SQL语法：

INSERT INTO table_name ( field1, field2,...fieldN )
      VALUES
      ( value1, value2,...valueN );

如果数据是字符型，必须使用单引号或者双引号，如："value"。
通过命令提示窗口插入数据
以下我们将使用 SQL INSERT INTO 语句向 MySQL 数据表 tutorials_tbl 插入数据
实例
以下实例中我们将想 tutorials_tbl 表插入三条数据:

root@host# mysql -u root -p password;
Enter password:*******

mysql> use TUTORIALS;
Database changed
mysql> INSERT INTO tutorials_tbl 
  ->(tutorial_title, tutorial_author, submission_date)
  ->VALUES
  ->("Learn PHP", "John Poul", NOW());
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO tutorials_tbl
  ->(tutorial_title, tutorial_author, submission_date)
  ->VALUES
  ->("Learn MySQL", "Abdul S", NOW());
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO tutorials_tbl
  ->(tutorial_title, tutorial_author, submission_date)
  ->VALUES
  ->("JAVA Tutorial", "Sanjay", '2007-05-06');
Query OK, 1 row affected (0.01 sec)
mysql>

注意：使用箭头标记(->)不是SQL语句的一部分，它仅仅表示一个新行，如果一条SQL语句太长，我们可以通过回车键来创建一个新行来编写SQL语句，SQL语句的命令结束符为分号（;）。
在以上实例中，我们并没有提供 tutorial_id 的数据，因为该字段我们在创建表的时候已经设置它为 AUTO_INCREMENT(自动增加) 属性。所以，该字段会自动递增而不需要我们去设置。实例中 NOW() 是一个 MySQL 函数，该函数返回日期和时间。
使用PHP脚本插入数据
你可以使用PHP 的 mysql_query() 函数来执行 SQL INSERT INTO命令来插入数据。
该函数有两个参数，在执行成功时返回 TRUE，否则返回 FALSE。
语法

bool mysql_query( sql, connection );

20151111105708111.png (742×100)

实例
以下实例中程序接收用户输入的三个字段数据，并插入数据表中：

<html>
<head>
<title>Add New Record in MySQL Database</title>
</head>
<body>
<&#63;php
if(isset($_POST['add']))
{
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('Could not connect: ' . mysql_error());
}

if(! get_magic_quotes_gpc() )
{
 $tutorial_title = addslashes ($_POST['tutorial_title']);
 $tutorial_author = addslashes ($_POST['tutorial_author']);
}
else
{
 $tutorial_title = $_POST['tutorial_title'];
 $tutorial_author = $_POST['tutorial_author'];
}
$submission_date = $_POST['submission_date'];

$sql = "INSERT INTO tutorials_tbl ".
  "(tutorial_title,tutorial_author, submission_date) ".
  "VALUES ".
  "('$tutorial_title','$tutorial_author','$submission_date')";
mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
 die('Could not enter data: ' . mysql_error());
}
echo "Entered data successfully\n";
mysql_close($conn);
}
else
{
&#63;>
<form method="post" action="<&#63;php $_PHP_SELF &#63;>">
<table width="600" border="0" cellspacing="1" cellpadding="2">
<tr>
<td width="250">Tutorial Title</td>
<td>
<input name="tutorial_title" type="text" id="tutorial_title">
</td>
</tr>
<tr>
<td width="250">Tutorial Author</td>
<td>
<input name="tutorial_author" type="text" id="tutorial_author">
</td>
</tr>
<tr>
<td width="250">Submission Date [ yyyy-mm-dd ]</td>
<td>
<input name="submission_date" type="text" id="submission_date">
</td>
</tr>
<tr>
<td width="250"> </td>
<td> </td>
</tr>
<tr>
<td width="250"> </td>
<td>
<input name="add" type="submit" id="add" value="Add Tutorial">
</td>
</tr>
</table>
</form>
<&#63;php
}
&#63;>
</body>
</html>

在我们接收用户提交的数据时，为了数据的安全性我们需要使用 get_magic_quotes_gpc() 函数来判断特殊字符的转义是否已经开启。如果这个选项为off（未开启），返回0，那么我们就必须调用addslashes 这个函数来为字符串增加转义。
义。
你也可以添加其他检查数据的方法，比如邮箱格式验证，电话号码验证，是否为整数验证等。

查询数据
MySQL 数据库使用SQL SELECT语句来查询数据。
你可以通过 mysql> 命令提示窗口中在数据库中查询数据，或者通过PHP脚本来查询数据。
语法
以下为在MySQL数据库中查询数据通用的 SELECT 语法：

SELECT field1, field2,...fieldN table_name1, table_name2...
[WHERE Clause]
[OFFSET M ][LIMIT N]

查询语句中你可以使用一个或者多个表，表之间使用逗号(,)分割，并使用WHERE语句来设定查询条件。
SELECT 命令可以读取一条或者多条记录。
你可以使用星号（*）来代替其他字段，SELECT语句会返回表的所有字段数据
你可以使用 WHERE 语句来包含任何条件。
你可以通过OFFSET指定SELECT语句开始查询的数据偏移量。默认情况下偏移量为0。
你可以使用 LIMIT 属性来设定返回的记录数。
通过命令提示符获取数据
以下实例我们将通过 SQL SELECT 命令来获取 MySQL 数据表 tutorials_tbl 的数据：
实例
以下实例将返回数据表tutorials_tbl的所有记录:

root@host# mysql -u root -p password;
Enter password:*******

mysql> use TUTORIALS;
Database changed
mysql> SELECT * from tutorials_tbl 
+-------------+----------------+-----------------+-----------------+
| tutorial_id | tutorial_title | tutorial_author | submission_date |
+-------------+----------------+-----------------+-----------------+
|   1 | Learn PHP  | John Poul  | 2007-05-21  |
|   2 | Learn MySQL | Abdul S   | 2007-05-21  |
|   3 | JAVA Tutorial | Sanjay   | 2007-05-21  |
+-------------+----------------+-----------------+-----------------+
3 rows in set (0.01 sec)

mysql>

使用PHP脚本来获取数据
使用PHP函数的mysql_query()及SQL SELECT命令来获取数据。
该函数用于执行SQL命令，然后通过 PHP 函数 mysql_fetch_array() 来使用或输出所有查询的数据。
mysql_fetch_array() 函数从结果集中取得一行作为关联数组，或数字数组，或二者兼有返回根据从结果集取得的行生成的数组，如果没有更多行则返回 false。
以下实例为从数据表 tutorials_tbl 中读取所有记录。
实例
尝试以下实例来显示数据表 tutorials_tbl 的所有记录。

<&#63;php
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT tutorial_id, tutorial_title, 
    tutorial_author, submission_date
  FROM tutorials_tbl';

mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
 die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_array($retval, MYSQL_ASSOC))
{
 echo "Tutorial ID :{$row['tutorial_id']} <br> ".
   "Title: {$row['tutorial_title']} <br> ".
   "Author: {$row['tutorial_author']} <br> ".
   "Submission Date : {$row['submission_date']} <br> ".
   "--------------------------------<br>";
} 
echo "Fetched data successfully\n";
mysql_close($conn);
&#63;>

以上实例中，读取的每行记录赋值给变量$row，然后再打印出每个值。
注意：记住如果你需要在字符串中使用变量，请将变量置于花括号。
在上面的例子中，PHP mysql_fetch_array()函数第二个参数为MYSQL_ASSOC，设置该参数查询结果返回关联数组，你可以使用字段名称来作为数组的索引。
PHP提供了另外一个函数mysql_fetch_assoc(), 该函数从结果集中取得一行作为关联数组。返回根据从结果集取得的行生成的关联数组，如果没有更多行，则返回 false。
实例
尝试以下实例，该实例使用了mysql_fetch_assoc()函数来输出数据表tutorial_tbl的所有记录：

<&#63;php
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT tutorial_id, tutorial_title, 
    tutorial_author, submission_date
  FROM tutorials_tbl';

mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
 die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_assoc($retval))
{
 echo "Tutorial ID :{$row['tutorial_id']} <br> ".
   "Title: {$row['tutorial_title']} <br> ".
   "Author: {$row['tutorial_author']} <br> ".
   "Submission Date : {$row['submission_date']} <br> ".
   "--------------------------------<br>";
} 
echo "Fetched data successfully\n";
mysql_close($conn);
&#63;>

你也可以使用常量 MYSQL_NUM 作为PHP mysql_fetch_array()函数的第二个参数，返回数字数组。
实例
以下实例使用MYSQL_NUM参数显示数据表tutorials_tbl的所有记录:

<&#63;php
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT tutorial_id, tutorial_title, 
    tutorial_author, submission_date
  FROM tutorials_tbl';

mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
 die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_array($retval, MYSQL_NUM))
{
 echo "Tutorial ID :{$row[0]} <br> ".
   "Title: {$row[1]} <br> ".
   "Author: {$row[2]} <br> ".
   "Submission Date : {$row[3]} <br> ".
   "--------------------------------<br>";
}
echo "Fetched data successfully\n";
mysql_close($conn);
&#63;>

以上三个实例输出结果都一样。
内存释放
在我们执行完SELECT语句后，释放游标内存是一个很好的习惯。。可以通过PHP函数mysql_free_result()来实现内存的释放。
以下实例演示了该函数的使用方法。
实例
尝试以下实例:

<&#63;php
$dbhost = 'localhost:3036';
$dbuser = 'root';
$dbpass = 'rootpassword';
$conn = mysql_connect($dbhost, $dbuser, $dbpass);
if(! $conn )
{
 die('Could not connect: ' . mysql_error());
}
$sql = 'SELECT tutorial_id, tutorial_title, 
    tutorial_author, submission_date
  FROM tutorials_tbl';

mysql_select_db('TUTORIALS');
$retval = mysql_query( $sql, $conn );
if(! $retval )
{
 die('Could not get data: ' . mysql_error());
}
while($row = mysql_fetch_array($retval, MYSQL_NUM))
{
 echo "Tutorial ID :{$row[0]} <br> ".
   "Title: {$row[1]} <br> ".
   "Author: {$row[2]} <br> ".
   "Submission Date : {$row[3]} <br> ".
   "--------------------------------<br>";
}
mysql_free_result($retval);
echo "Fetched data successfully\n";
mysql_close($conn);
&#63;>

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