SELECT items.*, quantity_table.quantity1 FROM items JOIN quantity_table WHERE id_item = 3 AND id_quant = 1

select i.id_item as item_id, name as item_name, type as item_type, qty as item_qty
from accounts as a
inner join equipment as e
  on a.id_acc = e.id_acc
inner join items as i
  on e.id_item = i.id_item
where a.id_acc = 1

CREATE TABLE item_quantity(
id_item INT NOT NULL,
id_quant INT NOT NULL,
CONSTRAINT id_item_quantity PRIMARY KEY (id_item,id_quant),
CONSTRAINT fk_id_item FOREIGN KEY (id_item)
    REFERENCES items(id_item),
CONSTRAINT fk_id_quant FOREIGN KEY (id_quant)
    REFERENCES quantity_table(id_quant));

SELECT items.id_item,items.name,quantity_table.quantity FROM item_quantity Inner Join items ON item_quantity.fk_id_item = items.id_item Inner Join quantity_table ON item_quantity.fk_id_quant = quantity_table.id_quant