Magento 2 Implement Declarative Schema in Custom Module.

In this post, I’ll explain to you how to Implement Declarative Schema in the Custom Module.

To implement declarative schema in a custom module you need to create db_schema.xml file inside /Vendor/Modulename/etc and write the following code.

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <table name="vendor_tablename" resource="default" engine="innodb" comment="Vendor Modulename">
        <column xsi:type="smallint" name="id" padding="6" unsigned="false" nullable="false" identity="true" comment="ID"/>
        <column xsi:type="varchar" name="author_name" nullable="false" length="25" comment="Name"/>
        <column xsi:type="varchar" name="email" nullable="false" length="25" comment="Email"/>
        <column xsi:type="varchar" name="description" nullable="false" length="255" comment="Descrition"/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="id"/>
        </constraint>
    </table>
</schema>

Use for create and set table names.

<table> .. </table>

Use for create and set columns of the table.

<column> .. </column>

Use for set constraint as like primary key, foreign key, unique key, etc.

<constraint> .. </constraint>

Before running the upgrade command you need to add your schema to db_whitelist_schema.json file by running the following command:

php bin/magento setup:db-declaration:generate-whitelist --module-name=Vendor_Modulename

Now, there are db_whitelist_schema.json file will be created in /Vendor/Modulename/etc folder.
Now, run

php bin/magento s:up

Now the table will be created inside the database.

In case if you want to rename a column, you will need to do few code changes in below line your db_schema.xml at appropriate column.

<column xsi:type="varchar" name="customer_email" onCreate="migrateDataFrom(email)" on_update="false" nullable="false" default="" comment="Customer Email"/>

Here, name=”customer_email” is a new column name and onCreate=”migrateDataFrom(email)” email is old column name.

Also, if you want to drop table, then you can either remove entire table node from an XML file or you can set a disabled attribute to true as like below line in your db_schema.xml

<table name="Vendor_Modulename" resource="default" engine="innodb" comment="Vendor Modulename" disabled="true">
 ..
 </table>

That’s it.

I hope this post helped you to find what you were looking for. Bookmark it for your future reference. Do comment below if you have any other questions on that.

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