Verify your knowledge

• On PostgreSQL 15 and PostgreSQL, is it possible to make DDL as a normal user?

  No it’s not possible. See the PostgreSQL and the public schema section for more details.

• What is the psql command to list all the databases with their sizes?

  postgres=# \l+  
  

  See the Confirming the database size section for more details.

• If the table is defined as the following:

  create table mytable (id integer,city_name varchar(60)); 
  

  The question is, does the following query show all records for which the city_name field is null?

  select * from mytable where city_name = ''; 
  

  No it doesn’t. The correct query is:

  select * from mytable where city_name is null; 
  

  See the NULL values section for more details.

• Can we create a new database, taking an existing one as a starting point?

  Yes, we can. We can use the TEMPLATE option...