在mysql中选择连续的记录块

Question

我在MySql 5中有一个电话号码表.简单的结构是

Accounts
id varchar(32) NOT NULL

记录如下

27100070000
27100070001
27100070002
27100070003
27100070004
27100070005
27100070008
27100070009
27100070012
27100070015
27100070016
27100070043

我需要对这些数据进行排序,并将连续的数字块分组到数字范围内.我愿意在C#LINQ中实现解决方案,但服务器端MySql是一等奖.在MySql中是否有一种方法可以汇总这些数据,以便输出如下所示？

Start       | End
-------------------------
27100070000 | 27100070005
27100070008 | 27100070009
27100070012 | 27100070015
27100070016 | NULL
27100070043 | NULL

Answer 1

有一个简单的技巧可以将连续的条目折叠到一个组中.如果按(row_number - entry)分组,则连续的条目将最终位于同一组中.这是一个展示我的意思的例子:

查询:

SELECT phonenum, @curRow := @curRow + 1 AS row_number, phonenum - @curRow
from phonenums p
join (SELECT @curRow := 0) r

结果:

|    PHONENUM | ROW_NUMBER | PHONENUM - @CURROW |
-------------------------------------------------
| 27100070000 |          1 |        27100069999 |
| 27100070001 |          2 |        27100069999 |
| 27100070002 |          3 |        27100069999 |
| 27100070003 |          4 |        27100069999 |
| 27100070004 |          5 |        27100069999 |
| 27100070005 |          6 |        27100069999 |
| 27100070008 |          7 |        27100070001 |
| 27100070009 |          8 |        27100070001 |
| 27100070012 |          9 |        27100070003 |
| 27100070015 |         10 |        27100070005 |
| 27100070016 |         11 |        27100070005 |
| 27100070040 |         12 |        27100070028 |

注意连续的条目如何具有相同的值PHONENUM - @CURROW.如果我们对该列进行分组,并选择每个组的最小值和最大值,则会有摘要(有一个例外:如果需要,可以用NULLSTART = END 替换END值):

查询:

select min(phonenum), max(phonenum) from
(
  SELECT phonenum, @curRow := @curRow + 1 AS row_number
  from phonenums p
  join (SELECT @curRow := 0) r
) p
group by phonenum - row_number

结果:

| MIN(PHONENUM) | MAX(PHONENUM) |
---------------------------------
|   27100070000 |   27100070005 |
|   27100070008 |   27100070009 |
|   27100070012 |   27100070012 |
|   27100070015 |   27100070016 |
|   27100070040 |   27100070040 |

演示:http://www.sqlfiddle.com/#!2/ 59b04/5