SELECT o.orderid, 
       o.orderqty,
       s.stockqty,
       'stocks are not enough' AS message 
FROM orders o
JOIN stocks s ON o.stockid = s.stockid
WHERE o.orderqty < s.stockqty

请看这把小提琴，如果有用请告诉我。
https://www.db-fiddle.com/f/hgednyettuxamxna9ell3p/2

CREATE TABLE t_stock (
  stockid INT,
  stockname VARCHAR(50),
  stockqty BIGINT
);
INSERT INTO t_stock (stockid, stockname, stockqty) VALUES (1, 'salmon', 150);
INSERT INTO t_stock (stockid, stockname, stockqty) VALUES (2, 'asparagus', 275);
INSERT INTO t_stock (stockid, stockname, stockqty) VALUES (3, 'lemon', 300);

CREATE TABLE t_order (
  orderid INT,
  orderqty BIGINT,
  stockid INT
);
INSERT INTO t_order (orderid, orderqty, stockid) VALUES (13, 150, 3);
INSERT INTO t_order (orderid, orderqty, stockid) VALUES (14, 275, 2);
INSERT INTO t_order (orderid, orderqty, stockid) VALUES (15, 300, 1);

SELECT o.orderid
      ,o.stockid
      ,o.orderqty
      ,s.stockqty
      ,CONCAT(CASE WHEN o.orderqty > s.stockqty
                   THEN 'stocks are not enough for '
                   WHEN o.orderqty = s.stockqty
                   THEN 'stocks are just enough for '
                   ELSE 'we have plenty of stock for '
                   END, s.stockname) as stockqty_analysis
  FROM t_stock s INNER JOIN t_order o
    ON s.stockid = o.stockid;