选择连续出现多次的记录

Question

我的问题是我想select一些连续出现的记录。例如，我们有这样的 table：

x
x
x
y
y
x
x
y

查询应该给出这样的答案：

Answer 1

SQL 表表示无序集。如果有一列指定顺序，您的问题才有意义。如果是这样，您可以使用行号差来确定组，然后聚合：

select col1, count(*)
from (select t.*,
             row_number() over (order by <ordering col>) as seqnum,
             row_number() over (partition by col1 order by <ordering col>) as seqnum_2
      from t
     ) t
group by col1, (seqnum - seqnum_2)

Answer 2

房间里的大象是缺少确定行顺序的列。

SELECT col1, count(*)
FROM  (
   SELECT col1, order_column
        , row_number() OVER (ORDER BY order_column)
        - row_number() OVER (PARTITION BY col1 ORDER BY order_column) AS grp
   FROM tbl
   ) t
GROUP  BY col1, grp
ORDER  BY min(order_column);

要排除只有一行的分区，请添加 HAVING 子句：

SELECT col1, count(*)
FROM  (
   SELECT col1, order_column
        , row_number() OVER (ORDER BY order_column)
        - row_number() OVER (PARTITION BY col1 ORDER BY order_column) AS grp
   FROM tbl
   ) t
GROUP  BY col1, grp
HAVING count(*) > 1
ORDER  BY min(order_column);

db<>fiddle here

添加最后的 ORDER BY 以保持原始顺序（和有意义的结果）。您可能还想添加像 min(order_column) 这样的列。

相关：

Select longest continuous sequence
Group by repeating attribute

Answer 3

我做了一个SQLFiddle http://sqlfiddle.com/#!18/f8900/5

CREATE TABLE [dbo].[SomeTable](
    [data] [nchar](1) NULL,
    [id] [int] IDENTITY(1,1) NOT NULL
);

INSERT INTO SomeTable
    ([data])
VALUES
    ('x'),
    ('x'),
    ('x'),
    ('y'),
    ('y'),
    ('x'),
    ('x'),
    ('y')
;

select * from SomeTable;

WITH SomeTable_CTE (Data, total, BaseId, NextId)
AS
(
SELECT 
    Data,
    1 as total,
    Id as BaseId,
    Id+1 as NextId
    FROM SomeTable
        where not exists(
            Select * from SomeTable Previous
            where Previous.Id+1 = SomeTable.Id 
            and Previous.Data = SomeTable.Data)
UNION ALL
select SomeTable_CTE.Data, SomeTable_CTE.total+1, SomeTable_CTE.BaseId as BaseId, SomeTable.Id+1 as NextId
from SomeTable_CTE inner join SomeTable on
SomeTable.Data = SomeTable_CTE.Data
and 
SomeTable.Id = SomeTable_CTE.NextId
)
SELECT Data, max(total)   as total
FROM SomeTable_CTE
group by Data, BaseId
order by BaseId

选择连续出现多次的记录

Selecting records that appear several times in a row

sql

gaps-and-islands