Php 我想在数据库中的3表，采购表，销售表和库存表

我正在将数据插入采购字段。现在我想要库存表，以后当我从销售表中销售产品时，我想要更新库存

我的控制器

public function add_purchase() {
    $data = array();

    $data['maincontent'] = $this->load->view('pages/add_purchase', $data, true);
    $this->load->view('master', $data);
}

public function save_purchase() {
    $this->Super_Admin_Model->save_purchase_info();
    redirect('Super_Admin/add_purchase');
}

我的模型

public function save_purchase_info() {
    $data = array();
    $data['material_id']=  $this->input->post('material_id',true);
    $data['pur_date']=  $this->input->post('pur_date',true);
    $data['pur_qty']=  $this->input->post('pur_qty',true);
    $data['unit_id'] = $this->input->post('unit_id', true);
    $data['pur_unit_price']=  $this->input->post('pur_unit_price',true);
    $data['total_price']=  $this->input->post('total_price',true);

    $this->db->insert('tbl_purchase', $data);
}

我的看法

<div>
    <form role="form" action="<?php echo base_url()?>Super_Admin/save_purchase.html" method="post">
        <div class="box-body">
            <div class="form-group">
                <label for="material_name">material Name</label>
                <select name="material_id">
                <option>Select Material</option>
                <?php $view_material_info=$this->Super_Admin_Model->select_all_material(); ?>
                <?php foreach ($view_material_info as $v_material) { ?>
                    <option value="<?php echo $v_material->material_id ?>"><?php echo $v_material->material_name ?></option>
                <?php } ?>
                </select>
            </div>
            <div class="form-group">
                <label for="date">Date</label>
                <input type="date" class="form-control" name="pur_date" id="" placeholder="Enter date">
            </div>
            <div class="form-group">
                <label for="quantity">Purchase Quantity</label>
                <input type="number" class="form-control" name="pur_qty" id="qty" placeholder="Enter Quantity">
            </div>

            <div class="form-group">
                <label for="unit_name">Unit Name</label>
                <select name="unit_id">
                    <option>Select Unit</option>
                    <?php $view_unit_info=$this->Super_Admin_Model->select_all_unit(); ?>
                    <?php foreach ($view_unit_info as $v_unit) { ?>
                        <option value="<?php echo $v_unit->unit_id ?>"><?php echo $v_unit->unit_name ?></option>
                    <?php } ?>
                </select>
            </div>
            <div class="form-group">
                <label for="unit_price">Unit_price</label>
                <input type="text" class="form-control" name="pur_unit_price" id="unit_price" placeholder="Enter price" oninput="calculate()">
            </div>
            <div class="form-group">
                <label for="total_price">Total_price</label>
                <input type="text" class="form-control" name="total_price" id="result" placeholder="Enter price">
            </div>

        </div>
        <!-- /.box-body -->
        <script>
            function calculate() {
                var my_qty = document.getElementById('qty').value;
                var my_price = document.getElementById('unit_price').value;
                var result = document.getElementById('result');
                var myResult = my_qty * my_price;
                result.value = myResult;

            }
        </script>
        <button type="submit" class="btn btn-primary">Save </button>
    </form>
</div>

检查这个，它会有帮助的-

purchase_tbl -
purchase_id | product_id | product_quantity | purchase_unit | purchase_date

stock_tbl
stock_id | product_id |  current_stock

sale_tbl
sale_id | product_id | product_quantity_sale | sale_unit | sale_date