In PostgreSQL, a generated column is a special type of column whose values are automatically calculated based on expressions or values from other columns. A generated column is referred to as a computed column in the SQL Server or a virtual column in Oracle .

There are two kinds of generated columns: Stored: A stored generated column is calculated when it is inserted or updated and occupies storage space. Virtual: A virtual generated column is computed when it is read and does not occupy storage space.

A virtual generated column is like a view, whereas a stored generated column is similar to a materialized view. Unlike a material view, PostgreSQL automatically updates data for stored generated columns.

PostgreSQL currently implements only stored generated columns.

In PostgreSQL, a sequence is a database object that allows you to generate a sequence of unique integers. Typically, you use a sequence to generate a unique identifier for a primary key in a table. Additionally, you can use a sequence to generate unique numbers across tables. To create a new sequence, you use the CREATE SEQUENCE statement.

Listing all sequences in a database To list all sequences in the current database, you use the following query: SELECT relname sequence_name FROM pg_class WHERE relkind = 'S';