sql server in built variable to capture the output code example

Example 1: postgresql print sessions using the database

select pid as process_id, 
       usename as username, 
       datname as database_name, 
       client_addr as client_address, 
       application_name,
       backend_start,
       state,
       state_change
from pg_stat_activity;

Example 2: sql run multiple updates in one query

UPDATE table_name
SET   field_name = 
      case  field_name2 
      when 'value' then 'change_to'
      when 'value2' then 'change_to2'
end