gistfile1.txt

CREATE TABLE item_sizes(
size_id text PRIMARY KEY
);
INSERT INTO  item_sizes VALUES ('small'), ('large');

CREATE TABLE warehouses(
warehouse_id SERIAL PRIMARY KEY,
name text NOT NULL
);

INSERT INTO warehouses(name) VALUES ('CA'), ('NY'), ('TX');

CREATE TABLE warehouses_sizes(
warehouse_id int NOT NULL REFERENCES warehouses,
size_id text NOT NULL REFERENCES item_sizes,
PRIMARY KEY(warehouse_id, size_id)
);

INSERT INTO warehouses_sizes(warehouse_id, size_id) VALUES 
(1, 'small'),
(1, 'large'),
(2, 'small'),
(3, 'large');

CREATE TABLE items(
item_id SERIAL PRIMARY KEY,
name text NOT NULL,
item_size text NOT NULL REFERENCES item_sizes
);

INSERT INTO items(name, item_size)
VALUES ('lamp', 'small'), ('sofa', 'large'), ('chair', 'large');
--------------------------------------
SELECT i.*
  FROM items AS i
 WHERE EXISTS (
       SELECT 1
          FROM warehouses_sizes AS ws
          JOIN warehouses AS w
            ON w.warehouse_id = ws.warehouse_id
         WHERE ws.size_id = i.item_size 
           AND w.name = 'CA'
           );