《SQL 进阶教程》 自连接排序

子查询所做的，是计算出价格比自己高的记录的条数并将其作为自己的位次

-- 自连接实现排序功能
SELECT P1.name,
P1.price,
(SELECT COUNT(P2.price)
FROM Products P2
WHERE P2.price > P1.price) + 1 AS rank_1
FROM Products P1
ORDER BY rank_1;

SELECT P1.name,
P1.price,
(SELECT COUNT(DISTINCT P2.price)
FROM Products P2
WHERE P2.price > P1.price) + 1 AS rank_1
FROM Products P1
ORDER BY rank_1;

-- 排序：使用自连接
SELECT P1.name,
MAX(P1.price) AS price,
COUNT(P2.name) +1 AS rank_1
FROM Products P1 LEFT OUTER JOIN Products P2
ON P1.price < P2.price
GROUP BY P1.name
ORDER BY rank_1;