Mysql 比较行SQL计数值的差异

我有一张桌子：

id     firstval    secondval     
1         4            5
2         5            4
3         3            3
4         6            6
5         7            8
6         9            8
7         3            3
8         3            3

我需要做的第一件事是计算secondval>firstval的次数。这显然没有问题

然而，我正在努力解决的问题是如何计算secondval>firstval的每个实例的下一行满足条件secondval 因此，在本例中，有两行将满足第一个规则id 1和5，第二个规则有两行，下一行id 2和6

SELECT id, @prevGreater AND secondval < firstval AS discrepancy, 
       @prevGreater := secondval > firstval AS secondGreater
FROM (SELECT * FROM YourTable ORDER BY id) AS x
CROSS JOIN (SELECT @prevGreater := false) AS init

现在，您可以根据需要使用COUNT语句：

DECLARE @YourTable TABLE 
(id int, firstval int, secondval int)

INSERT INTO @YourTable
SELECT 1, 4, 5
UNION ALL
SELECT 2, 5, 4
UNION ALL
SELECT 3, 3, 3
UNION ALL
SELECT 4, 6, 6
UNION ALL
SELECT 5, 7, 8
UNION ALL
SELECT 6, 9, 8
UNION ALL
SELECT 7, 3, 3
UNION ALL
SELECT 8, 3, 3

SELECT  ID
,CASE 
    WHEN SECONDVAL>FIRSTVAL THEN 0
    WHEN FIRSTVAL>SECONDVAL THEN 1
    ELSE 0
END AS DISCREPANCY
,CASE 
    WHEN SECONDVAL>FIRSTVAL THEN 1
    WHEN FIRSTVAL>SECONDVAL THEN 0
    ELSE 0
END AS SECONDGREATER

FROM    @YourTable

---

你可以试试这个。

谢谢。我将其初始化为false，否则第一行可能会被视为不一致，即使没有上一行可比较。这可能更有意义，是的。如果ID号中存在差异，该怎么办？此查询如何比较连续行？看看这把小提琴，它在第8行报告了一个不一致的地方，而它本不应该这样。

DECLARE @YourTable TABLE 
(id int, firstval int, secondval int)

INSERT INTO @YourTable
SELECT 1, 4, 5
UNION ALL
SELECT 2, 5, 4
UNION ALL
SELECT 3, 3, 3
UNION ALL
SELECT 4, 6, 6
UNION ALL
SELECT 5, 7, 8
UNION ALL
SELECT 6, 9, 8
UNION ALL
SELECT 7, 3, 3
UNION ALL
SELECT 8, 3, 3

SELECT  ID
,CASE 
    WHEN SECONDVAL>FIRSTVAL THEN 0
    WHEN FIRSTVAL>SECONDVAL THEN 1
    ELSE 0
END AS DISCREPANCY
,CASE 
    WHEN SECONDVAL>FIRSTVAL THEN 1
    WHEN FIRSTVAL>SECONDVAL THEN 0
    ELSE 0
END AS SECONDGREATER

FROM    @YourTable