Unable to create table with foreign key?

Question

<table name="profile_products" resource="default" engine="innodb" comment="profile products">
        
        <column xsi:type="smallint" name="id" unsigned="false" nullable="false" identity="true"
                comment="ID"/>
                
        <column xsi:type="int" name="product_id" unsigned="true" nullable="false" 
        identity="false" comment="Product ID"/>
        
        <column xsi:type="int" name="profile_id" nullable="false"  comment="Account code"/>
        
        <column xsi:type="int" name="account_id" nullable="false"  comment="Account code"/>
    

        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="id"/>
        </constraint>
        <constraint xsi:type="foreign" referenceId="ONBUY_PROFILE_PRODUCT_PROFILE_ID_ONBUY_PROFILE_ID" table="onbuy_profile_products"
            column="profile_id" referenceTable="onbuy_profile" referenceColumn="id"
               onDelete="CASCADE"/>

        <constraint xsi:type="foreign" referenceId="ONBUY_PROFILE_PRD_PRD_ID_CAT_PRD_ENTT_ENTT_ID" table="onbuy_profile_products"
            column="product_id" referenceTable="catalog_product_entity" referenceColumn="entity_id"
               onDelete="CASCADE"/>
       

        <constraint xsi:type="unique" referenceId="ONBUY_PROFILE_PRODUCT_PRODUCT_ID_PROFILE_ID">
            <column name="profile_id"/>
            <column name="product_id"/>
        </constraint>
       
        <index referenceId="ONBUY_PROFILE_PRODUCT_PROFILE_ID" indexType="btree">
           <column name="profile_id"/>
        </index>

        <index referenceId="ONBUY_PROFILE_PRD_PRD_ID" indexType="btree">
           <column name="product_id"/>
        </index>
              
    </table>

Answer 1

Create a foreign key In the following example, the selected constraint node defines the characteristics of the FL_ALLOWED_SEVERITIES foreign key.

<schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                 xsi:noNamespaceSchemaLocation="urn:magento:framework:Setup/Declaration/Schema/etc/schema.xsd">
    <table name="declarative_table">
        <column xsi:type="int" name="id_column" padding="10" unsigned="true" nullable="false" comment="Entity Id"/>
        <column xsi:type="int" name="severity" padding="10" unsigned="true" nullable="false" comment="Severity code"/>
        <column xsi:type="varchar" name="title" nullable="false" length="255" comment="Title"/>
        <column xsi:type="timestamp" name="time_occurred" padding="10" comment="Time of event"/>
        <constraint xsi:type="primary" referenceId="PRIMARY">
            <column name="id_column"/>
        </constraint>
       <constraint xsi:type="foreign" referenceId="FL_ALLOWED_SEVERITIES" table="declarative_table"
               column="severity" referenceTable="severities" referenceColumn="severity_identifier"
               onDelete="CASCADE"/>
    </table>
</schema>

You can also refer to the dev docs.

Thanks