<p><a href="https://aws.amazon.com/rds/aurora/dsql/">Amazon Aurora DSQL</a> now lets you add foreign key constraints to new and existing tables. Aurora DSQL is a serverless, distributed SQL database with PostgreSQL compatibility and active-active multi-Region availability.</p>
<p>You can now express your application's rules about how tables reference each other as FOREIGN KEY constraints in your Aurora DSQL cluster. Declare, for example, that a customer's primary address must reference an existing row in your address table. Aurora DSQL then refuses any write that would leave that customer pointing at an address that no longer exists.&nbsp;You choose what happens when a referenced row is deleted or updated, with the options NO ACTION, RESTRICT, CASCADE, SET NULL, and SET DEFAULT.</p>
<p>This feature is available in all <a href="https://aws.amazon.com/about-aws/global-infrastructure/regional-product-services/">AWS Regions</a> where Aurora DSQL is available. To learn more, see <a href="https://docs.aws.amazon.com/aurora-dsql/latest/userguide/working-with-foreign-key-constraints.html">working with foreign key constraints</a> and the <a href="https://docs.aws.amazon.com/aurora-dsql/latest/userguide/create-table-syntax-support.html#create-table-foreign-keys">CREATE TABLE foreign key syntax</a> in the Aurora DSQL User Guide.</p>