Dataset (query builder 19)

The query result of the database is also a data set. By default, the data set type is a two-dimensional array, but it can support returning a data set object, using the fetchCollection method:

// 获取数据集
$users = Db::name('user')->fetchCollection()->select();
// 遍历数据集
foreach($users as $user){
    echo $user['name'];
    echo $user['id'];
}

The returned data set object is think\Collection, which provides the same usage as arrays, and also encapsulates some additional methods.

When performing data set queries in the model, all data set objects are returned, but the think\model\Collection class (inherited from think\Collection) is used, but the usage is consistent.

You can directly use arrays to operate data set objects, for example:

// 获取数据集
$users = Db::name('user')->fetchCollection()->select();
// 直接操作第一个元素
$item  = $users[0];
// 获取数据集记录数
$count = count($users);
// 遍历数据集
foreach($users as $user){
    echo $user['name'];
    echo $user['id'];
}

The fetchCollection method also supports passing in the custom collection class name (must inherit think\Collection).

It should be noted that if you want to judge whether the data set is empty, you cannot directly use empty to judge, but must use the isEmpty method of the data set object to judge, for example:

$users = Db::name('user')->fetchCollection()->select();
if($users->isEmpty()){
    echo '数据集为空';
}

Collection class contains The following main methods: