What is the method for querying the value of a specified field in thinkphp

Step 1: Connect to the database

Before using ThinkPHP for database query, you must first configure the database connection information in the configuration file. Find the database.php configuration file in the conf directory and configure the database connection information

return [
    // 数据库类型
    'type'     => 'mysql',
    // 服务器地址
    'hostname' => 'localhost',
    // 数据库名
    'database' => 'test',
    // 用户名
    'username' => 'root',
    // 密码
    'password' => '',
    // 端口
    'hostport' => '3306',
    // 数据库编码默认采用utf8
    'charset'  => 'utf8',
];

Step 2: Query the value of the specified field

Use ThinkPHP to query the specified field The value of is very simple. We can use the select method to query the value of a specified field. For example, we have a user table that contains id, username and password. To query the usernames of all users, you can use the following code:

// 创建一个User模型实例
$user = new \app\model\User();
// 查询所有用户的用户名
$usernames = $user->field('username')->select();
// 打印用户名
foreach ($usernames as $username) {
    echo $username[&#39;username&#39;] . "<br/>";
}

In the above code, we first create a User model instance. Then, we use the field method to specify the field name we want to query. Finally, we use the select method to query the value of the specified field. In the foreach loop, we printed each username.

Step 3: Query the value of a specified field in a single record

Sometimes, we only need to query the value of a specified field in a single record. We can use the find method to achieve this operation. For example, if we want to query the username of the user with id 1, we can use the following code:

// 创建一个User模型实例
$user = new \app\model\User();
// 查询id为1的用户的用户名
$username = $user->where('id', 1)->value('username');
// 打印用户名
echo $username;

In the above code, we first create a User model instance. Then, we use the where method to specify the record with id equal to 1. Finally, we use the value method to get the value of the username field.

Step 4: Limit the number of query results

Normally, we do not need to query the specified fields in all records. We can use the limit method to limit the number of query results. For example, if we only want to query the usernames of the first 10 users, we can use the following code:

// 创建一个User模型实例
$user = new \app\model\User();
// 查询前10个用户的用户名
$usernames = $user->field('username')->limit(10)->select();
// 打印用户名
foreach ($usernames as $username) {
    echo $username[&#39;username&#39;] . "<br/>";
}

In the above code, we use the limit method to specify the number of query results to be 10.

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