In PostgreSQL, domains are basically data types with optional constraints. We can create them as a kind of user-defined data type, and then reuse them in our columns going forward.

As with any user-created object, we sometimes need to see a list of existing domains in a PostgreSQL database. Listing all domains can be useful for database management, documentation, or troubleshooting.

This article will show you how to retrieve a list of all domains in your PostgreSQL database.

Whenever we create a table in PostgreSQL, a composite type is automatically created behind the scenes. This composite type is based on the table that we created. Each column in the table becomes a field in the composite type.

If the table already uses a composite type, then the composite type that PostgreSQL creates will include that type in its definition, thereby creating a situation where we effectively have a nested composite type.

When we have a column with composite data in PostgreSQL, we can access each field by using dot notation. This is true whether we select the data or update it. This means that we can use dot notation to update individual fields within a composite column.

And if we need to update all fields at once, we can use the ROW constructor.