SELECT user_id FROM users
Array
(
[0] => Array
(
[user_id] => 441309419
)
[1] => Array
(
[user_id] => 246722435
)
[2] => Array
(
[user_id] => 285998042
)
[3] => Array
(
[user_id] => 313310029
)
}
Array
(
[0] => 441309419
[1] => 246722435
[2] => 285998042
[3] => 313310029
}