How to Create Setup, Upgrade, Uninstall Script in Magento 2

php bin/magento setup:upgrade

<?php

namespace Mageplaza\HelloWorld\Setup;

class InstallSchema implements \Magento\Framework\Setup\InstallSchemaInterface
{

	public function install(\Magento\Framework\Setup\SchemaSetupInterface $setup, \Magento\Framework\Setup\ModuleContextInterface $context)
	{
		$installer = $setup;
		$installer->startSetup();
		if (!$installer->tableExists('mageplaza_helloworld_post')) {
			$table = $installer->getConnection()->newTable(
				$installer->getTable('mageplaza_helloworld_post')
			)
				->addColumn(
					'post_id',
					\Magento\Framework\DB\Ddl\Table::TYPE_INTEGER,
					null,
					[
						'identity' => true,
						'nullable' => false,
						'primary'  => true,
						'unsigned' => true,
					],
					'Post ID'
				)
				->addColumn(
					'name',
					\Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
					255,
					['nullable => false'],
					'Post Name'
				)
				->addColumn(
					'url_key',
					\Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
					255,
					[],
					'Post URL Key'
				)
				->addColumn(
					'post_content',
					\Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
					'64k',
					[],
					'Post Post Content'
				)
				->addColumn(
					'tags',
					\Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
					255,
					[],
					'Post Tags'
				)
				->addColumn(
					'status',
					\Magento\Framework\DB\Ddl\Table::TYPE_INTEGER,
					1,
					[],
					'Post Status'
				)
				->addColumn(
					'featured_image',
					\Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
					255,
					[],
					'Post Featured Image'
				)
				->addColumn(
					'created_at',
					\Magento\Framework\DB\Ddl\Table::TYPE_TIMESTAMP,
					null,
					['nullable' => false, 'default' => \Magento\Framework\DB\Ddl\Table::TIMESTAMP_INIT],
					'Created At'
				)->addColumn(
					'updated_at',
					\Magento\Framework\DB\Ddl\Table::TYPE_TIMESTAMP,
					null,
					['nullable' => false, 'default' => \Magento\Framework\DB\Ddl\Table::TIMESTAMP_INIT_UPDATE],
					'Updated At')
				->setComment('Post Table');
			$installer->getConnection()->createTable($table);

			$installer->getConnection()->addIndex(
				$installer->getTable('mageplaza_helloworld_post'),
				$setup->getIdxName(
					$installer->getTable('mageplaza_helloworld_post'),
					['name', 'url_key', 'post_content', 'tags', 'featured_image'],
					\Magento\Framework\DB\Adapter\AdapterInterface::INDEX_TYPE_FULLTEXT
				),
				['name', 'url_key', 'post_content', 'tags', 'featured_image'],
				\Magento\Framework\DB\Adapter\AdapterInterface::INDEX_TYPE_FULLTEXT
			);
		}
		$installer->endSetup();
	}
}

<?php

namespace Mageplaza\HelloWorld\Setup;

use Magento\Framework\Setup\InstallDataInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;

class InstallData implements InstallDataInterface
{
	protected $_postFactory;

	public function __construct(\Mageplaza\HelloWorld\Model\PostFactory $postFactory)
	{
		$this->_postFactory = $postFactory;
	}

	public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
	{
		$data = [
			'name'         => "How to Create SQL Setup Script in Magento 2",
			'post_content' => "In this article, we will find out how to install and upgrade sql script for module in Magento 2. When you install or upgrade a module, you may need to change the database structure or add some new data for current table. To do this, Magento 2 provide you some classes which you can do all of them.",
			'url_key'      => '/magento-2-module-development/magento-2-how-to-create-sql-setup-script.html',
			'tags'         => 'magento 2,mageplaza helloworld',
			'status'       => 1
		];
		$post = $this->_postFactory->create();
		$post->addData($data)->save();
	}
}

<?php
namespace Mageplaza\HelloWorld\Setup;

use Magento\Framework\Setup\UpgradeSchemaInterface;
use Magento\Framework\Setup\SchemaSetupInterface;
use Magento\Framework\Setup\ModuleContextInterface;

class UpgradeSchema implements UpgradeSchemaInterface
{
	public function upgrade( SchemaSetupInterface $setup, ModuleContextInterface $context ) {
		$installer = $setup;

		$installer->startSetup();

		if(version_compare($context->getVersion(), '1.2.0', '<')) {
			$installer->getConnection()->addColumn(
				$installer->getTable( 'mageplaza_helloworld_post' ),
				'test',
				[
					'type' => \Magento\Framework\DB\Ddl\Table::TYPE_DECIMAL,
					'nullable' => true,
					'length' => '12,4',
					'comment' => 'test',
					'after' => 'status'
				]
			);
		}



		$installer->endSetup();
	}
}

<?php

namespace Mageplaza\HelloWorld\Setup;

use Magento\Framework\Setup\UpgradeDataInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;
use Magento\Framework\Setup\ModuleContextInterface;

class UpgradeData implements UpgradeDataInterface
{
	protected $_postFactory;

	public function __construct(\Mageplaza\HelloWorld\Model\PostFactory $postFactory)
	{
		$this->_postFactory = $postFactory;
	}

	public function upgrade(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
	{
		if (version_compare($context->getVersion(), '1.2.0', '<')) {
			$data = [
				'name'         => "Magento 2 Events",
				'post_content' => "This article will talk about Events List in Magento 2. As you know, Magento 2 is using the events driven architecture which will help too much to extend the Magento functionality. We can understand this event as a kind of flag that rises when a specific situation happens. We will use an example module Mageplaza_HelloWorld to exercise this lesson.",
				'url_key'      => '/magento-2-module-development/magento-2-events.html',
				'tags'         => 'magento 2,mageplaza helloworld',
				'status'       => 1
			];
			$post = $this->_postFactory->create();
			$post->addData($data)->save();
		}
	}
}

<?php
namespace Mageplaza\HelloWorld\Setup;

use Magento\Framework\Setup\UninstallInterface;
use Magento\Framework\Setup\SchemaSetupInterface;
use Magento\Framework\Setup\ModuleContextInterface;

class Uninstall implements UninstallInterface
{
	public function uninstall(SchemaSetupInterface $setup, ModuleContextInterface $context)
	{
		$installer = $setup;
		$installer->startSetup();

		$installer->getConnection()->dropTable($installer->getTable('mageplaza_helloworld_post'));

		$installer->endSetup();
	}
}