Number of records queried by php

Number of records queried by PHP

When we use PHP to write a database query script, it is very important to accurately obtain the number of records in the database. This article will introduce how to get the number of records in the database in PHP.

Using the SQL COUNT function

In most cases, we use the SQL COUNT function to count the number of records in the database. In PHP, we can easily achieve this through the COUNT function in the SELECT statement.

For example, the following PHP code is used to count the number of records in a database table:

<?php
// 设置数据库连接
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = mysqli_connect($servername, $username, $password, $dbname);

// 检查连接是否成功
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

// 使用 SQL COUNT 函数统计记录数
$sql = "SELECT COUNT(*) FROM myTable";
$result = mysqli_query($conn, $sql);

// 检查是否获得查询结果
if (!$result) {
  die("Query failed: " . mysqli_error($conn));
}

// 处理查询结果
$row = mysqli_fetch_row($result);
echo "记录总数为：" . $row[0];

// 关闭数据库连接
mysqli_close($conn);
?>

Function using the result set object

MySQLi and PDO extension libraries provide some Function, you can directly obtain the number of records in the query result set, for example:

• mysqli_num_rows() — Get the number of records in the MySQLi result set.
• PDOStatement::rowCount() — Get the number of records in the PDO result set.

The following is an example of using the MySQLi extension library:

<?php
// 设置数据库连接
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = mysqli_connect($servername, $username, $password, $dbname);

// 检查连接是否成功
if (!$conn) {
  die("Connection failed: " . mysqli_connect_error());
}

// 查询数据库
$sql = "SELECT * FROM myTable";
$result = mysqli_query($conn, $sql);

// 检查查询结果
if (!$result) {
  die("Query failed: " . mysqli_error($conn));
}

// 获取结果集中的记录数
$num_rows = mysqli_num_rows($result);

// 输出记录总数
echo "记录总数为：" . $num_rows;

// 关闭数据库连接
mysqli_close($conn);
?>

The example of using the PDO extension library is as follows:

<?php
// 设置数据库连接
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);

// 定义查询语句
$sql = "SELECT * FROM myTable";

// 执行查询，获取结果集
$result = $conn->query($sql);

// 获取结果集中的记录数
$num_rows = $result->rowCount();

// 输出记录总数
echo "记录总数为：" . $num_rows;

// 关闭数据库连接
$conn = null;
?>

Summary

Whether using The SQL COUNT function, or a function using a result set object, can obtain the number of records in the database. Which method to use depends on your personal preference and the needs of your project. If your query results already contain all records, it is more convenient to use the functions of the result set object directly. However, if you only need to get the number of records, try to use the COUNT function, because this can reduce the amount of data transmission and processing, thereby improving query efficiency.

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