create table products
( id smallint not null primary key auto_increment
, name varchar(11)
);
insert into products ( name ) values 
 ( 'shampoo' ), ( 'beer' ), ( 'underwear' ), ( 'toothpaste' )
;
create table categories
( id smallint not null primary key 
, name varchar(11)
);
insert into categories ( id, name ) values 
 ( 101,'food' )
,( 102,'drink' )
,( 103,'clothing' )
,( 104,'essential' )
,( 105,'luxury' )
;
create table productcategories
( product_id smallint not null 
, category_id smallint not null 
, foreign key ( product_id ) references products ( id )
, foreign key ( category_id ) references categories ( id )
, primary key ( product_id, category_id )
);
insert into productcategories values 
 ( 1, 105 )
,( 2, 102 )
,( 2, 104 )
,( 3, 103 )
,( 4, 105 )
;
select products.name   as product
     , categories.name as category
  from products
left outer
  join productcategories
    on products.id 
     = productcategories.product_id
left outer
  join categories
    on productcategories.category_id 
     = categories.id
order
    by product
     , category
;
product    category
beer       drink
beer       essential
shampoo    luxury
toothpaste luxury
underwear  clothing