Explain named constraints in the createtable.md and altertable.md pages

content/references/sqlreference/statements/altertable.md

@@ -12,6 +12,32 @@ See [PostgreSQL: ALTER TABLE](https://www.postgresql.org/docs/current/sql-altert
 ```sql
 ALTER TABLE IF EXISTS movies RENAME COLUMN runlength TO duration;
 ```
-Rename column of table with `table_name` and `current_column_name` to the `new_column_name`. 
+Rename column of table with `table_name` and `current_column_name` to the `new_column_name`.
 If exists checks if the table exists and only tries to rename in the case of existence.
 
+## Constraint statements
+
+#### `ADD CONSTRAINT`
+
+Adds a constraint to an existing table.
+CedarDB supports named `primary key`, `foreign key`, and `unique` constraints:
+
+```sql
+ALTER TABLE orders ADD CONSTRAINT orders_pk primary key (id);
+ALTER TABLE orders ADD CONSTRAINT orders_customer_fk foreign key (customer) references customers (id);
+ALTER TABLE orders ADD CONSTRAINT orders_unique unique (customer, item);
+```
+
+The `CONSTRAINT <name>` part can be omitted entirely, in which case CedarDB automatically assigns a default name using the same conventions as PostgreSQL:
+- Primary key: `tablename_pkey`
+- Unique: `tablename_colname_key`
+- Foreign key: `tablename_colname_fkey`
+
+#### `DROP CONSTRAINT`
+
+Removes a constraint by name, using either an explicit name or the default name:
+
+```sql
+ALTER TABLE orders DROP CONSTRAINT orders_unique;
+ALTER TABLE orders DROP CONSTRAINT orders_pkey;
+```

content/references/sqlreference/statements/createtable.md

@@ -33,6 +33,28 @@ multiple columns:
 * `foreign key(...) references other_table(...)`
 * `not null`
 
+The `unique`, `primary key`, and `foreign key` constraints can optionally be given a name using the `constraint` keyword:
+
+```sql
+create table orders (
+    id        int,
+    customer  int,
+    item      int,
+    constraint orders_pk primary key (id),
+    constraint orders_customer_fk foreign key (customer) references customers (id),
+    constraint orders_item_fk foreign key (item) references items (id),
+    constraint orders_unique unique (customer, item)
+);
+```
+
+The `constraint <name>` part can be omitted entirely, in which case CedarDB automatically assigns a default name using the same conventions as PostgreSQL:
+- Primary key: `tablename_pkey`
+- Unique: `tablename_colname_key`
+- Foreign key: `tablename_colname_fkey`
+
+These default names can be used just like explicit names, e.g., to drop a constraint with `alter table ... drop constraint <name>`.
+Naming is not supported for `not null`.
+
 ## Options
 
 Create a temporary table that will be dropped when the current client disconnects: