Magento2 : How to show custom tables fields to system configuration drop down

Question

I am developing custom module, I want to display tables fields to system configuration drop down.

How to get all tables fields and set it to in drop down for system configuration.

Thanks

Answer 1

Just create system.xml file,

app/code/Packagename/SystemConfig/etc/adminhtml/system.xml,

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
 <system>
 <tab id="nis" translate="label" sortOrder="200">
 <label>NIS</label>
 </tab>
 <section id="nis" translate="label" type="text" sortOrder="40" showInDefault="1" showInWebsite="1" showInStore="1">
 <label>Configuration</label>
 <tab>nis</tab>
 <resource>Packagename_SystemConfig::config_nis</resource>
 <group id="fields_list" translate="label" type="text" sortOrder="90" showInDefault="1" showInWebsite="1" showInStore="1">
 <field id="table_field" translate="label comment" type="select" sortOrder="6" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
 <label>Table field</label>
 <source_model>Packagename\SystemConfig\Model\Config\Source\Tablefield</source_model>
 </field>
 </group>
 </section>
 </system>
</config>

app/code/Packagename/SystemConfig/Model/Config/Source/Tablefield.php

<?php
namespace Packagename\SystemConfig\Model\Config\Source;
class Tablefield implements \Magento\Framework\Option\ArrayInterface
{
 public function __construct(
 \Magento\Framework\App\ResourceConnection $resource
 ) {
 $this->_resource = $resource;
 }
 /**
 * Retrieve option values array
 *
 * @return array
 */
 public function toOptionArray()
 {
 $options = [];
 $options[] = ['label' => __('Table Field'), 'value' => 'tablefield'];
 foreach ($this->getTablefield() as $field) {
 $options[] = ['label' => $field['COLUMN_NAME'], 'value' => $field['COLUMN_NAME']];
 }
 return $options;
 }
 public function getTablefield(){
 $connection = $this->_resource->getConnection(\Magento\Framework\App\ResourceConnection::DEFAULT_CONNECTION);
 $customTable = $connection->getTableName('sales_order');
 /* you can change your magento dabase name below */
 $allField = $connection->fetchAll("SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'magento2' AND TABLE_NAME = '".$customTable."'"); //magento2 is database name
 return $allField;
 }
}