thinkphp5 discusses how to determine whether an MQL object is empty

When using the MQL object in ThinkPHP5, we sometimes need to determine whether the object is empty. This article will explore how to determine whether an MQL object is empty.

1. What is an MQL object
   The MQL (Model Query Language) object is an instance of the basic model class Query in ThinkPHP5, which is used to build query conditions and operations for the database.

In ThinkPHP5, each model has a default MQL object. We can obtain this object through the static method of the model, such as:

$userModel = new \app\user\model\UserModel;
$userModel->where('username', 'like', '%admin%')->select();

can also be written as:

$userModel = \app\user\model\UserModel::where('username', 'like', '%admin%')->select();

2. Determine whether the MQL object is empty
   When operating the database, we sometimes encounter the situation where the query result is empty. At this time, we need to determine whether the MQL object is empty. There are several judgment methods:

• Judgment by count() method

The MQL object provides the count() method for querying records that meet the conditions. quantity. If the number of records returned is 0, the MQL object is empty.

$userModel = \app\user\model\UserModel::where('username', 'like', '%notexist%');
if($userModel->count() == 0){
    echo 'MQL对象为空';
}

• Judging by the find() method

The MQL object provides the find() method to query the first record that meets the conditions. If the returned result is null, it means that the MQL object is empty.

$userModel = \app\user\model\UserModel::where('username', 'like', '%notexist%')->find();
if(is_null($userModel)){
    echo 'MQL对象为空';
}

• Judging by the select() method

The MQL object provides the select() method to query all records that meet the conditions. If the returned result is an empty array, it means that the MQL object is empty.

$userModel = \app\user\model\UserModel::where('username', 'like', '%notexist%')->select();
if(empty($userModel)){
    echo 'MQL对象为空';
}

• Judging by the isEmpty() method

The MQL object provides the isEmpty() method, which is used to determine whether the MQL object is empty. If the return result is true, it means that the MQL object is empty.

$userModel = \app\user\model\UserModel::where('username', 'like', '%notexist%');
if($userModel->isEmpty()){
    echo 'MQL对象为空';
}

3. Summary
   When using the MQL object of ThinkPHP5, we need to often determine whether the MQL object is empty. This article introduces four judgment methods, which are judged through the count(), find(), select() and isEmpty() methods. Choosing an appropriate judgment method can make the code more concise and elegant, and at the same time improve the running efficiency of the code.

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