PHP mysqli_result data_seek()方法

 PHP MySQLi 函数

PHP mysqli_result::data_seek() / mysqli_data_seek() 函数用于将结果指针调整为任意值结果集中偏移量指定的行。

语法

//面向对象风格
public mysqli_result::data_seek(offset)

//面向过程风格
mysqli_data_seek(result, offset)

参数

返回值

成功时返回 true，成功时返回 false

示例:面向对象风格

下面的示例展示了mysqli_result::data_seek()方法的用法。

<?php
//建立与数据库的连接
$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: ". $mysqli->connect_error;
  exit();
}

//从数据库获取查询结果
$sql = "SELECT Name, Age FROM Employee ORDER BY Age";
$result = $mysqli->query($sql);

//寻找行号51
$result->data_seek(50);

//获取单行
$row = $result->fetch_row();

printf("Name: %s, Age: %d\n", $row[0], $row[1]);

//关闭连接
$mysqli->close();
?>

上述代码的输出将类似于:

Name: John, Age: 28

示例:面向过程风格

下面的示例显示mysqli_data_seek()的用法 函数。

<?php
//建立与数据库的连接
$mysqli = mysqli_connect("localhost", "user", "password", "database");
if (mysqli_connect_errno()) {
  echo "Failed to connect to MySQL: ". mysqli_connect_error();
  exit();
}

//从数据库获取查询结果
$sql = "SELECT Name, Age FROM Employee ORDER BY Age";
$result = mysqli_query($mysqli, $sql);

//寻找行号51
mysqli_data_seek($result, 50);

//获取单行
$row = mysqli_fetch_row($result);

printf("Name: %s, Age: %d\n", $row[0], $row[1]);

//关闭连接
mysqli_close($mysqli);
?>

上述代码的输出将类似于:

Name: John, Age: 28

示例:迭代时调整结果指针

当迭代结果集以强加自定义顺序或在迭代多次时倒回结果集时，此函数非常有用。考虑下面的示例:

<?php
//建立与数据库的连接
$mysqli = new mysqli("localhost", "user", "password", "database");
if ($mysqli->connect_errno) {
  echo "Failed to connect to MySQL: ". $mysqli->connect_error;
  exit();
}

//从数据库获取查询结果
$sql = "SELECT Name, Age FROM Employee ORDER BY Age";
$result = $mysqli->query($sql);

//逆序迭代结果集
for ($row_no = $result->num_rows - 1; $row_no >= 0; $row_no--) {
  $result->data_seek($row_no);

  //获取单行
  $row = $result->fetch_row();

  printf("Name: %s, Age: %d\n", $row[0], $row[1]);
}

//重置指针
//结果集的开头
$result->data_seek(0);

echo "\n";

//再次迭代相同的结果集
while ($row = $result->fetch_row()) {
  printf("Name: %s, Age: %d\n", $row[0], $row[1]);
}

//关闭连接
$mysqli->close();
?>

上述代码的输出将类似于:

Name: Adam, Age: 28
Name: John, Age: 27
Name: Kim, Age: 26
Name: Marry, Age: 23

Name: Marry, Age: 23
Name: Kim, Age: 26
Name: John, Age: 27
Name: Adam, Age: 28