Add References Target Primary Key By Default as a Postgres TIL

postgres/references-target-primary-key-by-default.md

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+# References Target Primary Key By Default
+
+Typically when I am creating a table or adding a column that involves a foreign
+key constraint, I explicitly name the reference column.
+
+```sql
+create table contacts (
+  id int generated always as identity primary key,
+  user_id int references users(id);
+);
+```
+
+The [Create Table PostgreSQL
+Docs](https://www.postgresql.org/docs/17/sql-createtable.html) point out that
+specifying the reference column isn't strictly necessary.
+
+> These clauses specify a foreign key constraint, which requires that a group
+> of one or more columns of the new table must only contain values that match
+> values in the referenced column(s) of some row of the referenced table. If
+> the refcolumn list is omitted, the primary key of the reftable is used.
+
+If we're using the primary key as the reference column, then we can choose to
+omit the reference column.
+
+```sql
+create table contacts (
+  id int generated always as identity primary key,
+  user_id int references users;
+);
+```
+
+In the same way we can do this when adding a column.
+
+```sql
+alter table contacts
+  add column account_id int references account;
+```