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错误号：1048
“btc”列不能为空
但实际上我发送的一切权利，我甚至尝试了参数与网址，但它仍然说，btc不能为空。怎么了

$date='';
        $timezone = "Asia/Karachi";
        if(function_exists('date_default_timezone_set'))
        date_default_timezone_set($timezone);
        $date=date('d-m-Y | H:i:s');
    $data=array(
        'username' => $this->session->userdata('username'),
        'btc' => $this->input->post('btc'),
        'networkfee' => $this->input->post('networkfee'),
        'address' => $this->input->post('address'),
        'riseupfee' => $this->input->post('riseupfee'),
        'date' => $date,
        'status' => 'Sent'
    );
    $this->load->model('ajax_model');
    $data = $this->ajax_model->withdraw_btc($data);

正在发送ajax请求。

$.ajax({
                type:'POST',
                data:{btc: '0.0001', address: 'xxxx', risupfee: '0.001', 
   networkfee: '0.0001'},
                url:'<?php echo site_url('ajax/withdraw_btc'); ?>',
                success: function(result){
                    alert(result);

                }