text: -- examples on comparison operators
  alter session set current_schema = hron;
  
  -- equality
  select *
  from region
  where region_id = 1;
  
  -- difference
  select *
  from region
  where region_id != 2;
  
  -- difference, alternative notation
  select *
  from region
  where region_id <> 2;
  
  -- strictly less than
  select *
  from region
  where region_id < 3;
  
  -- less or equal to
  select *
  from region
  where region_id <= 3;
  
  -- strictly bigger than
  select *
  from region
  where region_id > 3;
  
  -- greater or equal to
  select *
  from region
  where region_id >= 3;
  
  -- simple pattern matching
  -- "like" a string starting with one char, then "ull", then 0, 1 or more chars
  select first_name, last_name
  from employee
  where last_name like '_ull%';
  
  -- "like" a string having an "m" anywhere
  select name
  from region
  where name like '%m%';
  
  -- starting with "A"
  select first_name, last_name
  from employee
  where last_name like 'A%';
  
  -- ...
  select first_name, last_name
  from employee
  where last_name like '__ll%';
  
  -- ...
  select last_name
  from employee
  where last_name like '___';
  
  -- implicit cast to string before checking the pattern
  select last_name, first_name, hired
  from employee
  where hired like '%-21';
  
  select last_name, first_name, hired
  from employee
  where hired like '%-MAY-%';
  
  -- interval check with "between ... and ..."
  select *
  from region
  where region_id between 1 and 3;
  
  -- "between" strings
  select *
  from country
  where name between 'Belgium' and 'China';
  
  -- ...
  select *
  from country
  where name between 'I' and 'J';
  
  -- "between" dates
  select last_name, first_name, hired
  from employee
  where hired between date'2015-01-01' and date'2015-12-31';
  
  -- check if "in" a set
  select *
  from region
  where region_id in (4, 2, 1);
  
  -- "not like"
  -- not an "a" anywhere
  select name
  from region
  where name not like '%a%';
  
  -- check if (not) in a set
  select *
  from region
  where region_id not in (2, 4);
  
  -- beware of null
  select *
  from employee
  where commission not in (.30, null);
  
  -- "is (not) null" is the only way to check it
  select *
  from employee
  where commission is not null and commission != .30;
  
  -- this one works fine
  select *
  from employee
  where commission in (0.10, 0.15);
  
  -- can't compare a 'good' value with null
  select *
  from region
  where name not in (null) or name in (null);
  
  -- this one works as expected
  select *
  from region
  where name is not null or name is null;
  