在分组数据中查找连续范围

Question

我有一个具有以下结构的表：

CREATE TABLE `Rings` (
    ID_RingType CHAR(2),
    Number MEDIUMINT UNSIGNED,
    ID_User INT(11)
);

和数据：

INSERT INTO `Rings` VALUES
  ('AA',1,1),
  ('AA',2,1),
  ('AA',3,1),
  ('AA',11,1),
  ('AA',12,1),
  ('AA',13,1),
  ('AA',14,1),
  ('AA',15,1),
  ('AB',16,1),
  ('AB',17,1),
  ('AB',18,1),
  ('AB',19,1),
  ('AB',20,2),
  ('AB',21,2),
  ('AB',22,2);

我想组基于所述数据ID_User和ID_RingType和用于数字的每个连续范围列出MIN和MAX。

结果应如下所示：

ID_User | ID_RingType | MIN  | MAX
1       | 'AA'        | 1    | 3
1       | 'AA'        | 11   | 15
1       | 'AB'        | 16   | 19
2       | 'AB'        | 20   | 22

我浏览了关于这个主题的几篇文章，但无法调整它们以适合我的数据。

任何帮助，将不胜感激。

Answer 1

由于 MySQL 不支持ROW_NUMBER()，您可以使用变量来创建这样的组。

样本数据

CREATE TABLE `Rings` (
    ID_RingType CHAR(2),
    Number MEDIUMINT UNSIGNED,
    ID_User INT(11)
);

INSERT INTO `Rings` VALUES
  ('AA',1,1),
  ('AA',2,1),
  ('AA',3,1),
  ('AA',11,1),
  ('AA',12,1),
  ('AA',13,1),
  ('AA',14,1),
  ('AA',15,1),
  ('AB',16,1),
  ('AB',17,1),
  ('AB',18,1),
  ('AB',19,1),
  ('AB',20,2),
  ('AB',21,2),
  ('AB',22,2);

询问

SET @grp = 0;
SET @preNum = 0;

SELECT ID_User,ID_RingType,MIN(Number),MAX(Number) FROM
(
SELECT 
ID_RingType,
ID_User,
Number,
@grp := CASE WHEN Number = @preNum + 1   THEN @grp ELSE @grp + 1 END grp,
@preNum := Number 
FROM `Rings`
ORDER BY ID_RingType,ID_User,Number
)T
GROUP BY ID_RingType,ID_User,grp

输出

ID_User | ID_RingType | MIN  | MAX
1       | 'AA'        | 1    | 3
1       | 'AA'        | 11   | 15
1       | 'AB'        | 16   | 19
2       | 'AB'        | 20   | 22

Answer 2

变量的答案会更有效，但这里是纯 SQL 的答案：

select 
    a.id_user, 
    a.id_ringtype, 
    a.number      as min,
    min(b.number) as max
from 
    rings as a 
  join rings as b 
    on  a.id_user = b.id_user 
    and a.id_ringtype = b.id_ringtype 
    and a.number <= b.number 
where not exists 
      ( select 1 
        from rings as c 
        where c.id_user = a.id_user 
          and c.id_ringtype = a.id_ringtype 
          and c.number = a.number - 1
      )
  and not exists 
      ( select 1 
        from rings as d 
        where d.id_user = b.id_user 
          and d.id_ringtype = b.id_ringtype 
          and d.number = b.number + 1
      ) 
group by 
    a.id_user, 
    a.id_ringtype, 
    a.number ;

效率将取决于许多因素（主要是数据的分布），但索引(id_user, id_ringtype, number)对于此查询至关重要。