CREATE TABLE Classes (
  class varchar(20),
  type varchar(2),
  country varchar(20),
  numGuns int,
  bore int,
  displacement int
);
CREATE TABLE Battles (
  name varchar(20),
  date DATE
);
CREATE TABLE Outcomes (
  ship varchar(20),
  battle varchar(20),
  result varchar(20)
, sunkBy varchar(20));
CREATE TABLE Ships (
  name varchar(20),
  class varchar(20),
  launched int
);

WITH M AS(
  SELECT class from Ships
  GROUP BY class
  HAVING COUNT(class) > 1
)
SELECT ships.class, COUNT(*)
FROM Outcomes, Ships, m 
WHERE Outcomes.sunkby = Ships.name AND M.class = Ships.class
GROUP BY ships.class;

with x as (
   select ships.name, count(*) as c
   from ships, outcomes
   where ships.name = outcomes.sunkby
  group by ships.name
)
select ships.class, sum(x.c) as sunk, count(*) as class_size
from ships
left join x on (ships.name = x.name)
group by ships.class
having class_size > 1

stmt    : assn ';'
        | com
assn    : id '=' expr
expr    : id
        | numb
        | expr opr expr
        | '(' expr ')'
        | '(' '-' expr ')'
numb    : int
        | int '.' int
com     : '#' (string | epsilon)

select coalesce(1, 2);
>> 1

select coalesce(null, 2);
>> 2

select
case
   when x.c is null 
	then 0
   else x.c
end
from ....

       ResultSet rs = stmt.executeQuery( "SELECT XXX FROM XYZ;" );
	         while ( rs.next() ) 
	         {	        
	         String test = rs.getString("XXX");
	         }

Human(Id, gender, ...)
Man(Id, ...)
Woman(Id, ...)