SQL专家

是否有使用SQL将数据运行分组在一起的有效方法？
还是在代码中处理数据会更有效。

例如，如果我有以下数据：

ID|Name
01|Harry Johns
02|Adam Taylor
03|John Smith
04|John Smith
05|Bill Manning
06|John Smith

我需要显示以下内容：

Harry Johns
Adam Taylor
John Smith (2)
Bill Manning
John Smith

@Matt：对不起，我无法使用在预览中有效但无法在最终显示中使用的嵌入式html表格格式化数据。

解决方案

回答

对于这种特殊情况，我们要做的就是按名称分组并要求计数，如下所示：

select Name, count(*)
from MyTable
group by Name

这样一来，我们就可以将每个名称的计数作为第二列。

我们可以通过以下方式将其全部合并为一列：

select Name + ' (' + cast(count(*) as varchar) + ')'
from MyTable
group by Name

回答

好吧，这：

select Name, count(Id)
from MyTable
group by Name

会给你这个：

Harry Johns, 1
Adam Taylor, 1
John Smith, 2
Bill Manning, 1

这(MS SQL语法)：

select Name +
    case when ( count(Id) > 1 ) 
         then ' ('+cast(count(Id) as varchar)+')' 
         else ''
    end
from MyTable
group by Name

会给你这个：

Harry Johns
Adam Taylor
John Smith (2)
Bill Manning

我们是否真的想要结果结尾处的其他John Smith？

编辑：哦，我明白了，我们希望将连续运行分组。在这种情况下，我会说我们需要一个游标或者在程序代码中进行操作。

回答

试试这个：

select n.name, 
    (select count(*) 
     from myTable n1
     where n1.name = n.name and n1.id >= n.id and (n1.id <=
        (
        select isnull(min(nn.id), (select max(id) + 1 from myTable))
        from myTable nn
        where nn.id > n.id and nn.name <> n.name
        )
     ))
from myTable n
where not exists (
   select 1
   from myTable n3
   where n3.name = n.name and n3.id < n.id and n3.id > (
            select isnull(max(n4.id), (select min(id) - 1 from myTable))
            from myTable n4
            where n4.id < n.id and n4.name <> n.name
            )
)

我想那会做你想要的。虽然有点纠结。

！经过几次编辑后，我认为我已经整理了所有边缘情况。

回答

我满怀热情地讨厌游标...但这是一个狡猾的游标版本...

Declare @NewName Varchar(50)
Declare @OldName Varchar(50)
Declare @CountNum int
Set @CountNum = 0

DECLARE nameCursor CURSOR FOR 
SELECT Name
FROM NameTest
OPEN nameCursor

FETCH NEXT FROM nameCursor INTO @NewName

  WHILE @@FETCH_STATUS = 0 

    BEGIN

      if @OldName <> @NewName
      BEGIN
         Print @OldName + ' (' + Cast(@CountNum  as Varchar(50)) + ')'
         Set @CountNum = 0
      END
      SELECT @OldName = @NewName
      FETCH NEXT FROM nameCursor INTO @NewName
      Set @CountNum = @CountNum + 1

    END
Print @OldName + ' (' + Cast(@CountNum  as Varchar(50)) + ')'

CLOSE nameCursor
DEALLOCATE nameCursor

回答

这个怎么样：

declare @tmp table (Id int, Nm varchar(50));

insert @tmp select 1, 'Harry Johns';
insert @tmp select 2, 'Adam Taylor';
insert @tmp select 3, 'John Smith';
insert @tmp select 4, 'John Smith';
insert @tmp select 5, 'Bill Manning';
insert @tmp select 6, 'John Smith';

select * from @tmp order by Id;

select Nm, count(1) from 
(
select Id, Nm, 
    case when exists (
        select 1 from @tmp t2 
        where t2.Nm=t1.Nm 
        and (t2.Id = t1.Id + 1 or t2.Id = t1.Id - 1)) 
        then 1 else 0 end as Run
from @tmp t1
) truns group by Nm, Run

[编辑]可以缩短一点

select Nm, count(1) from (select Id, Nm, case when exists (
        select 1 from @tmp t2 where t2.Nm=t1.Nm 
        and abs(t2.Id-t1.Id)=1) then 1 else 0 end as Run
from @tmp t1) t group by Nm, Run

回答

我的解决方案只是踢(这是一个有趣的练习)，没有游标，没有迭代，但是我确实有一个辅助字段

-- Setup test table
DECLARE @names TABLE    (
                        id      INT                 IDENTITY(1,1),
                        name    NVARCHAR(25)        NOT NULL,
                        grp     UNIQUEIDENTIFIER    NULL
                        )

INSERT @names (name)
SELECT 'Harry Johns'    UNION ALL 
SELECT 'Adam Taylor'    UNION ALL
SELECT 'John Smith'     UNION ALL
SELECT 'John Smith'     UNION ALL
SELECT 'Bill Manning'   UNION ALL
SELECT 'Bill Manning'   UNION ALL
SELECT 'Bill Manning'   UNION ALL
SELECT 'John Smith'     UNION ALL
SELECT 'Bill Manning'   

-- Set the first id's group to a newid()
UPDATE      n
SET         grp = newid()
FROM        @names n
WHERE       n.id = (SELECT MIN(id) FROM @names)

-- Set the group to a newid() if the name does not equal the previous
UPDATE      n
SET         grp = newid()
FROM        @names n
INNER JOIN  @names b
        ON  (n.ID - 1) = b.ID
        AND ISNULL(b.Name, '') <> n.Name

-- Set groups that are null to the previous group
-- Keep on doing this until all groups have been set
WHILE (EXISTS(SELECT 1 FROM @names WHERE grp IS NULL))
BEGIN
    UPDATE      n
    SET         grp = b.grp
    FROM        @names n
    INNER JOIN  @names b
            ON  (n.ID - 1) = b.ID
            AND n.grp IS NULL
END

-- Final output
SELECT      MIN(id)     AS id_start,
            MAX(id)     AS id_end,
            name,
            count(1)    AS consecutive
FROM        @names
GROUP BY    grp, 
            name
ORDER BY    id_start

/*
Results:

id_start    id_end  name            consecutive
1           1       Harry Johns     1
2           2       Adam Taylor     1
3           4       John Smith      2
5           7       Bill Manning    3
8           8       John Smith      1
9           9       Bill Manning    1
*/