Postgresql generated columns

Stored

create table example
(
    id                                                  bigint generated always as identity,
    a                                      integer   ,
    b                                      integer   ,
    c                                      integer   GENERATED ALWAYS AS
                                                                      (CASE
                                                                          WHEN ((a IS NOT NULL) AND
                                                                                (b IS NOT NULL) AND
                                                                                (b > 0))
                                                                              THEN floor(((a / b))::double precision)
                                                                          ELSE NULL::double precision
                                                                          END) STORED
)

create table example
(
    id                                                  bigint generated always as identity,
    a                                      timestamp  not null ,
    b                                      char(4) GENERATED ALWAYS AS (EXTRACT(year FROM date))::text) STORED
)

Virtual column

create table example
(
    id                                                  bigint generated always as identity,
    a                                      integer   ,
    b                                      integer   ,
    c                                      integer   GENERATED ALWAYS AS
                                                                      (CASE
                                                                          WHEN ((a IS NOT NULL) AND
                                                                                (b IS NOT NULL) AND
                                                                                (b > 0))
                                                                              THEN floor(((a / b))::double precision)
                                                                          ELSE NULL::double precision
                                                                          END)
)

create table example
(
    id                                                  bigint generated always as identity,
    a                                      timestamp  not null ,
    b                                      char(4) GENERATED ALWAYS AS (EXTRACT(year FROM date))::text)
)