SQL SERVER IDENTITY vs POSTGRES SERIAL

What’s the POSTGRES equivalent of SQL SERVER’s IDENTITY column property?

SQL SERVER’s IDENTITY column property is often found when creating a table, and defining a column as int datatype (or biigint), with the IDENTITY property.

Create table dbo.some_table
(
  my_primary_key int IDENTITY as primary key
, some_field varchar(10)
);

The IDENTITY property helps auto-increment the field in SQL SERVER.

More details: MS link.

In POSTGRES, we follow a 2-step strategy.

1) Create (or alter) the table, and define the datatype as SERIAL.
Create table public.some_table
(
  my_primary_key SERIAL primary key
, some_field varchar(10)
);

In the background, POSTGRES then creates a SEQUENCE that is used for this SERIAL column
public.some_table_my_primary_key_seq

2) Grant USAGE and SELECT to the users (or roles) that will insert into the table.
The owner of the table has all privileges on the table, and the sequence.
Other users do not.
Make sure the other users (or roles) have select and insert on the table
GRANT SELECT, INSERT on public.some_table to <other_users>;

To correct this, execute the psql:
GRANT USAGE, SELECT on public.some_table_my_primary_key_seq to  <other_users>;
(replace <other_users> with the users/roles as needed)

If step (2) isn’t followed,  you are presented with an error message:

Query execution failed

Reason:
SQL Error [42501]: ERROR: permission denied for sequence some_table_my_primary_key_seq

(

in DBeaver, the error message looks like

)

Summary

In SQL SERVER, there’s the IDENTITY field property.

In POSTGRES, use SERIAL, and grant USAGE, and SELECT on the associated sequence.

Bonus tip

It may be easier to grant all privileges in a schema to the user.

grant all privileges on all sequences in schema public to some_user;

Script

--connect to postgres as user2 grant user2 to user1; –this is needed so that user1 can execute as user2 --reconnect to postgres as user1 select session_user, current_user, current_database(); Create table public.some_table --user1 owns this table (    my_primary_key SERIAL primary key , some_field varchar(10) ); grant select, insert on public.some_table to user2; set role user2;      select session_user, current_user, current_database();      select * from public.some_table;      insert into public.some_table (some_field) values ('hello'); --this should error      reset role; --reset the local user to user1;      select session_user, current_user, current_database(); --confirm that we're back as user1 grant usage, select on public.some_table_my_primary_key_seq to user2; set role user2;      select session_user, current_user, current_database();      select * from public.some_table;      insert into public.some_table (some_field) values ('hello'); --this should now pass      reset role; --reset the local user to user1;      select session_user, current_user, current_database(); --confirm that we're back as user1 drop table public.some_table; --can only drop the table as the owner user1