Columns are the small unity of a table and they define how data must be stored through their data types and additional attributes as shown in the image below.
Attribute | Description |
---|---|
Data Type |
This attribute handles the data type assigned to the column. |
Default Value |
This field defines the default value for the column in case of none is specified in a INSERT command. If user want to set up a simple expression use the attribute Expression. The attribute Sequence is used to configure a default value for serial data types based upon a sequence object. Once selected the sequence this object will be converted into an expression like: nextval('seq'::regclass) . The Identity attribute is used to configure an identity column (introduced in PostgreSQL 10). The possible values of this field are ALWAYS and BY DEFAULT . In newer versions it's possible to tweak the sequence parameters associated to the indentity column. |
NOT NULL |
Creates a NOT NULL constraint in the column. |
** Identity/Generated columns **
https://www.postgresql.org/docs/current/ddl-generated-columns.html