需求1:

SELECT COUNT(*) FROM 
 (SELECT * FROM abc GROUP BY col1) AS a;

执行代码

$sub = Abc::where(..)->groupBy(..); // Eloquent Builder instance

$count = DB::table( DB::raw("({$sub->toSql()}) as sub") )
    ->mergeBindings($sub->getQuery()) // you need to get underlying Query Builder
    ->count();

需求2: 执行如下代码

SELECT 
    `p`.`id`,
    `p`.`name`, 
    `p`.`img`, 
    `p`.`safe_name`, 
    `p`.`sku`, 
    `p`.`productstatusid` 
FROM `products` p 
WHERE `p`.`id` IN (
    SELECT 
        `product_id` 
    FROM `product_category`
    WHERE `category_id` IN ('223', '15')
)
AND `p`.`active`=1

实现:

Products::whereIn('id', function($query){
    $query->select('paper_type_id')
    ->from(with(new ProductCategory)->getTable())
    ->whereIn('category_id', ['223', '15'])
    ->where('active', 1);
})->get();

综合运用:

$query = \DB::table('message')
    ->where(function ($query) use ($userId) {
        $query->where([
            ['receiver_id', '=', "$userId"],
            ['type', '=', Messages::PRIVATE_MESSAGE],
        ]);
    });
if (!empty($groupIds)) {
    $query->orWhere(function ($queryq) use ($groupIds) {
        $queryq
            ->where([
                ['type', '=', Messages::GROUP_MESSAGE],
                ['message.created_at', '>', \Auth::user()->created_at]
            ])
            ->whereIn('receiver_id', $groupIds);
    });
}
/* 获取广播 */
$query->orWhere(function ($query) {
    $query
        ->where([
            ['type', '=', Messages::BROADCAST_MESSAGE],
            ['dead_line', '>', Carbon::createFromTimestamp(time())],
            ['message.created_at', '>', \Auth::user()->created_at]
        ]);
});
$query->leftJoin('message_log', function ($join) use ($userId) {
    $join->on('message.id', '=', 'message_log.message_id')
        ->where('message_log.user_id', '=', $userId);
})

    ->leftJoin('subscribe', function ($join)  use ($userId) {
        $join->on('subscribe.pcode_id', '=', 'message.receiver_id')
            ->where('subscribe.user_id', '=', $userId);
    })

    ->select([
        'message_log.id as message_log_id',
        'message.id as message_id',
        'message.content',
        'message.type',
        'message.sender_id',
        'message.updated_at',
        'message.created_at',
        'message.dead_line',
        \DB::raw('IF (message.`created_at` < subscribe.`created_at` , 1, 0) AS is_expired')
    ]);

$resQuery = \DB::table(\DB::raw("({$query->toSql()}) as sub"))
    ->mergeBindings($query)
    ->where('is_expired', '=', 0);