Example. Foreign Keys Constraints. Wrong Columns

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Page: https://www.postgresql.org/docs/18/ddl-constraints.html
Description:

https://www.postgresql.org/docs/current/ddl-constraints.html#DDL-CONSTRAINTS-FK

In the last example of this section it seems the `users` table is referenced
wrong.

```sql
CREATE TABLE users (
    tenant_id integer REFERENCES tenants ON DELETE CASCADE,
    user_id integer NOT NULL,
    PRIMARY KEY (tenant_id, user_id)
);

CREATE TABLE posts (
    tenant_id integer REFERENCES tenants ON DELETE CASCADE,
    post_id integer NOT NULL,
    author_id integer,
    PRIMARY KEY (tenant_id, post_id),
    FOREIGN KEY (tenant_id, author_id) REFERENCES users ON DELETE SET NULL
(author_id)
);
```

In this example `FOREIGN KEY (tenant_id, author_id) REFERENCES users ON
DELETE SET NULL (author_id)` implies that `users` table columns are named
`(tenant_id, author_id)` but in fact `users` table does not have a
`author_id` column.

That line should be probably like this because `users` tables has a
`user_id` column instead of `author_id`

```sql
CREATE TABLE posts (
    # ...
    FOREIGN KEY (tenant_id, author_id) REFERENCES users (tenant_id, user_id)
ON DELETE SET NULL (author_id)
);
```