我已更改为 while 循环以加快执行速度,但即使 while 循环对于以下查询也需要很长时间。请帮助我更改 while 循环以加快执行速度。我更新了描述以便更好地理解。
BEGIN
DECLARE @Modules TABLE
(
ID INT IDENTITY(1,1)
, ListElid NVARCHAR(250)
, ListType NVARCHAR(250)
, orderArray NVARCHAR(250)
, LeftTSMKEY NVARCHAR(250)
)
declare @orderArray int, @LeftTSMKEY nvarchar(250), @ListElid nvarchar(250), @ListType
nvarchar(250), @ListType_Prev nvarchar(250)
set @ListType_Prev=''
set @inc=0
INSERT INTO @Modules select ListElid, ListType,orderArray, LeftTSMKEY from QAT_ListElid order
by ListType,orderArray
DECLARE @Count INT, @Counter INT, @ListId NVARCHAR(250) --, @Listtype NVARCHAR(260), @orderArray
NVARCHAR(260) , @LeftTSMKEY NVARCHAR(260)
SELECT @Count = COUNT(*) FROM @Modules m
SET @Counter = 1
WHILE @Counter <= @Count
BEGIN
SELECT @ListId= ListElid, @Listtype = ListType , @orderArray = orderArray , @LeftTSMKEY =
LeftTSMKEY FROM @Modules m
WHERE ID = @Counter -- extracting values from the table by counternum
if @ListType<>@ListType_Prev
begin
set @inc=0
set @ListType_Prev =@ListType
end
Else If @ListType=@ListType_Prev
begin
set @inc=@inc+1
End
if @inc <> @orderArray
begin
INSERT [QAT_ListElid2] ([ListElid],[ListType],[orderArray],[LeftTSMKEY])
values (@ListElid,@ListType,@inc,@LeftTSMKEY+CAST(@inc as nvarchar(10))+']')
End
SET @Counter = @Counter + 1
END
end
可能是错误的,但看起来像是“间隙和岛屿”问题。
我们首先检查每一行是否与前一行具有相同的
ListType
。
然后我们为每个新的值延伸创建一个组编号。
然后我们得到一个在此分组上分区的行号。
WITH Previous AS (
SELECT *,
CASE WHEN ListType = LAG(ListType) OVER (ORDER BY ID) THEN 1 END SamePrevious
FROM QAT_ListElid
),
Grouped AS (
SELECT *,
COUNT(SamePrevious) OVER (ORDER BY ID ROWS UNBOUNDED PRECEDING) Grp
),
Numbered AS (
SELECT *,
ROWNUMBER() OVER (PARTITION BY Grp ORDER BY ID) - 1 rn
)
INSERT [QAT_ListElid2]
(ListElid, ListType, orderArray, LeftTSMKEY)
select
ListElid,
ListType,
rn,
LeftTSMKEY + CAST(rn as nvarchar(10)) + ']'
from Grouped
WHERE orderArray <> rn