Question

：）

有没有办法创建索引，并使用给定条件递增，但没有CURSOR处理/使用

例如：

sql_tables

我的情况是：“如果当前颜色（这是要检查的项目）与最后一个相同：不增加，否则以一个单位递增”

这必须在没有CURSOR USAGE的SQL查询中，当然是个好时机（至少使用10000行）

提前致谢。

编辑：我忘了提到NEW_INDEX列不存在。必须使用查询生成它。

EDIT2：有没有办法只使用SELECT / INSERT / UPDATE语句？（未设置，声明...）

Answer 1

假设一个名为Colors的表格分别包含ID，Color和ColorIndex类别的字段int，varchar和int。我还假设OP表示prev / after，基于ID字段中asc字段的排序。

您可以在没有光标的情况下执行此操作，并使用while循环...但它肯定不会基于：

DECLARE @MyID int
DECLARE @CurrentIndex int
DECLARE @CurrentColor varchar(50)
DECLARE @PreviousColor varchar(50)

SET @CurrentIndex = (SELECT 0)

SET @MyID = (SELECT TOP 1 ID FROM Colors ORDER BY ID ASC)
SET @CurrentColor = (SELECT '')
SET @PreviousColor = (SELECT Color FROM Colors WHERE ID = @MyID)

WHILE (@MyID IS NOT NULL)
 BEGIN
   IF (@CurrentColor <> @PreviousColor)
     BEGIN
        SET @PreviousColor = (SELECT Color FROM Colors WHERE ID = @MyID)
        SET @CurrentIndex = (SELECT @CurrentIndex + 1)
        UPDATE Colors SET ColorIndex = @CurrentIndex WHERE ID = @MyID
     END 
   ELSE
      BEGIN
        UPDATE Colors SET ColorIndex = @CurrentIndex WHERE ID = @MyID
        SET @PreviousColor = (SELECT Color FROM Colors WHERE ID = @MyID)
      END
 SET @MyID = (SELECT TOP 1 ID FROM Colors WHERE ID > @MyID ORDER BY ID ASC)
 SET @CurrentColor = (SELECT Color FROM Colors WHERE ID = @MyID)
 END

执行后的结果：

enter image description here

只要ID和颜色被编入索引，性能就不会太糟糕。好的一面是它比使用普通的旧CURSOR要快一点，并不像它那样邪恶。解决方案支持SQL 2000,2005和2008（因为您使用的是不支持CTE的SQL 2000）。

Answer 2

declare @ID int, 
        @MaxID int, 
        @NewIndex int, 
        @PrevCol varchar(50)

select @ID = min(ID),
       @MaxID = max(ID),
       @PrevCol = '',
       @NewIndex = 0       
from YourTable       

while @ID <= @MaxID
begin
  select @NewIndex = case when Colour = @PrevCol 
                       then @NewIndex 
                       else @NewIndex + 1 
                     end,
         @PrevCol = Colour
  from YourTable
  where ID = @ID

  update YourTable 
  set NewIndex = @NewIndex
  where ID = @ID

  set @ID = @ID + 1
end

http://data.stackexchange.com/stackoverflow/q/122958/

Answer 3

    select
        IDENTITY(int,1,1) as COUNTER
        ,c1.ID
    into
        #temp
    from
        CUSTOMERS c1
        left outer join (
                select
                    c1.ID, max(p.ID) as PRV_ID
                from
                    CUSTOMERS c1, 
                    (
                    select
                        ID
                    from
                        CUSTOMERS
                    ) p
                where
                    c1.ID > p.ID
                group by
                    c1.ID
                    ) k on k.ID = c1.ID
        left outer join CUSTOMERS p on p.ID = k.PRV_ID 
    where        
        ((c1.FAVOURITE_COLOUR < p.FAVOURITE_COLOUR)
         or
        (c1.FAVOURITE_COLOUR > p.FAVOURITE_COLOUR)
         or
         p.FAVOURITE_COLOUR is null)

    update
        CUSTOMERS
    set
        NEW_INDEX = i.COUNTER 
    --select *
    from    
        CUSTOMERS
        inner join (
            select 
                c1.ID, max(t.COUNTER) as COUNTER
            from
                CUSTOMERS c1, 
                (
                select
                    ID
                    ,COUNTER
                from
                    #temp
                ) t
            where
                c1.ID >= t.ID
            group by
                c1.ID
            ) i on i.ID = CUSTOMERS.ID

    drop table #temp

    select * from CUSTOMERS

SQL Server 2000：有条件地从列生成和递增数据而不使用CURSOR

3 个答案: