How to add Foreign Key in database table using Magento 2?

We can add a foreign key for a column of a table using Magento by the below code snippet.

Add foreign key in a column,
Example, you are creating a module and you want to add Store Filter in your module for that case you need to create a relation with store table.
Using below code snippet you can create a relationship with store table.

Here your custom table name is {my_table_name} and this table must contain field name store_id to a relation with store table.
In InstallSchema or UpgradeSchema File, you need to add below code snippet,

    $installer->getFkName('my_table_name', 'store_id', 'store', 'store_id'),
    $installer->getTable('store'), /* main table name */

“my_table_name” is your table name
“store_id” is your table field name to relate with parent table
“store” Main table to create relation with
“store_id” Main table field name
“ACTION_CASCADE” ¬†used for the type of actions which executes on a matched row of the child table when a parent table row gets update or delete action.

     * Actions used for foreign keys





Using Above code You can add foreign key in your table which contain relation to store table of Magento.

You can refer blog for add Index to column by How to add Index to table column using Magento 2?