i have a form it's like assign a product through frontend. but my doubt is after that how i validate
<form action="<?php echo $this->getUrl('mpassignproduct/index/edit') ?>" enctype="multipart/form-data" method="post" id="form-customer-product-edit">
<li class="fields">
<div class="customer-name">
<div class="field">
<label class="required" for="sku"><em>*</em><?php echo $helper->__('Sku')?></label>
<div class="input-box">
<input type="text" name="sku" id="sku" class="required-entry input-text" value="<?php echo $mpAssignProductModel->getsku() ?>"/></div></div></div></li>
</form>
i upload to this form and store it db my problem if same sku also upload how i restrict that.
