当值高于前一个值时选择范围

Question

如何获取值高于先前值的所有记录。例如，下表中的第一个范围从 id 1 开始，到 id 6 结束，下一个范围是从 7 到 10，等等......

id  Open
1   1.30077
2   1.30088
3   1.30115
4   1.30132
5   1.30135
6   1.30144
7   1.30132
8   1.30137
9   1.30152
10  1.30158
11  1.30149
12  ...

Answer 1

您的样本数据

USE test
DROP TABLE IF EXISTS rangedata;
CREATE TABLE rangedata
(
  id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
  open FLOAT
) ENGINE=MyISAM;
INSERT INTO rangedata (open) VALUES
(1.30077),(1.30088),(1.30115),(1.30132),
(1.30135),(1.30144),(1.30132),(1.30137),
(1.30152),(1.30158),(1.30149),
(1.30077),(1.30088),(1.30115),(1.30132),
(1.30135),(1.30144),(1.30132),(1.30137),
(1.30152),(1.30158),(1.30149),
(1.30077),(1.30088),(1.30115),(1.30132),
(1.30135),(1.30144),(1.30132),(1.30137),
(1.30152),(1.30158),(1.30149);

您的样本数据已加载

mysql>     USE test
Database changed
mysql>     DROP TABLE IF EXISTS rangedata;
Query OK, 0 rows affected (0.01 sec)

mysql>     CREATE TABLE rangedata
    ->     (
    ->       id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->       open FLOAT
    ->     ) ENGINE=MyISAM;
Query OK, 0 rows affected (0.09 sec)

mysql>     INSERT INTO rangedata (open) VALUES
    ->     (1.30077),(1.30088),(1.30115),(1.30132),
    ->     (1.30135),(1.30144),(1.30132),(1.30137),
    ->     (1.30152),(1.30158),(1.30149),
    ->     (1.30077),(1.30088),(1.30115),(1.30132),
    ->     (1.30135),(1.30144),(1.30132),(1.30137),
    ->     (1.30152),(1.30158),(1.30149),
    ->     (1.30077),(1.30088),(1.30115),(1.30132),
    ->     (1.30135),(1.30144),(1.30132),(1.30137),
    ->     (1.30152),(1.30158),(1.30149);
Query OK, 33 rows affected (0.00 sec)
Records: 33  Duplicates: 0  Warnings: 0

mysql>

使用连接查询

这是 LEFT JOIN 查询

SET @grp = 1;
SELECT A.open prev,(@grp:=@grp+IF(A.open<B.open,1,0)) group_number
FROM rangedata A LEFT JOIN rangedata B ON A.id= B.id+1;

这是它的输出

mysql> SELECT A.open prev,(@grp:=@grp+IF(A.open<B.open,1,0)) group_number
    -> FROM rangedata A LEFT JOIN rangedata B ON A.id= B.id+1;
+---------+--------------+
| prev    | group_number |
+---------+--------------+
| 1.30088 |            1 |
| 1.30115 |            1 |
| 1.30132 |            1 |
| 1.30135 |            1 |
| 1.30144 |            1 |
| 1.30132 |            2 |
| 1.30137 |            2 |
| 1.30152 |            2 |
| 1.30158 |            2 |
| 1.30149 |            3 |
| 1.30077 |            4 |
| 1.30088 |            4 |
| 1.30115 |            4 |
| 1.30132 |            4 |
| 1.30135 |            4 |
| 1.30144 |            4 |
| 1.30132 |            5 |
| 1.30137 |            5 |
| 1.30152 |            5 |
| 1.30158 |            5 |
| 1.30149 |            6 |
| 1.30077 |            7 |
| 1.30088 |            7 |
| 1.30115 |            7 |
| 1.30132 |            7 |
| 1.30135 |            7 |
| 1.30144 |            7 |
| 1.30132 |            8 |
| 1.30137 |            8 |
| 1.30152 |            8 |
| 1.30158 |            8 |
| 1.30149 |            9 |
| 1.30077 |            9 |
+---------+--------------+
33 rows in set (0.01 sec)

不带连接的查询

使用用户定义的变量，您只需监视每一行并查看前一个值何时更大。准备好询问了吗？这里是：

SET @prev = '0.00000';
SET @grp = 1;
SELECT id,open,(@grp:=@grp+increasing) group_number FROM
(SELECT id,open,IF(@prev<=open,0,1) increasing,(@prev:=open) FROM rangedata) A;

这是您的样本数据的三倍：

这是查询的执行：

mysql> SET @prev = '0.00000';
Query OK, 0 rows affected (0.00 sec)

mysql> SET @grp = 1;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT id,open,(@grp:=@grp+increasing) group_number FROM
    -> (SELECT id,open,IF(@prev<=open,0,1) increasing,(@prev:=open) FROM rangedata) A;
+----+---------+--------------+
| id | open    | group_number |
+----+---------+--------------+
|  1 | 1.30077 |            1 |
|  2 | 1.30088 |            1 |
|  3 | 1.30115 |            1 |
|  4 | 1.30132 |            1 |
|  5 | 1.30135 |            1 |
|  6 | 1.30144 |            1 |
|  7 | 1.30132 |            2 |
|  8 | 1.30137 |            2 |
|  9 | 1.30152 |            2 |
| 10 | 1.30158 |            2 |
| 11 | 1.30149 |            3 |
| 12 | 1.30077 |            4 |
| 13 | 1.30088 |            4 |
| 14 | 1.30115 |            4 |
| 15 | 1.30132 |            4 |
| 16 | 1.30135 |            4 |
| 17 | 1.30144 |            4 |
| 18 | 1.30132 |            5 |
| 19 | 1.30137 |            5 |
| 20 | 1.30152 |            5 |
| 21 | 1.30158 |            5 |
| 22 | 1.30149 |            6 |
| 23 | 1.30077 |            7 |
| 24 | 1.30088 |            7 |
| 25 | 1.30115 |            7 |
| 26 | 1.30132 |            7 |
| 27 | 1.30135 |            7 |
| 28 | 1.30144 |            7 |
| 29 | 1.30132 |            8 |
| 30 | 1.30137 |            8 |
| 31 | 1.30152 |            8 |
| 32 | 1.30158 |            8 |
| 33 | 1.30149 |            9 |
+----+---------+--------------+
33 rows in set (0.00 sec)

关键点是：每次出现新的组编号时，都会告诉您下一个删除的值。

请注意两个查询的输出是相同的

注意prev：如果和之间存在一些浮点问题，第二个查询不是完美的解决方案open。如果它们彼此非常接近，那可能是不对的。这是编写存储过程之外的最佳尝试。