我有一个平坦的、非规范化的表:
PRODUCT_ID LOCATION PARTNUMBER PRICE STATUS
1234567890 9999 5555 10.99 A
1234567890 8888 5555 11.99 A
1234567890 7777 5555 9.99 B
9876543210 9999 3333 15.99 A
9876543210 4444 3333 14.99 A
...
我需要查询它来生成一个输出文件,它看起来像这样:
1234567890|9999|5555|10.99|A,8888|5555|11.99|A,7777|5555|9.99|B
9876543210|9999|3333|15.99|A,4444|3333|14.99|A
...
所以基本上是一种数据格式:
产品_ID|LOCATION1|PARTNUMBER1|PRICE1|STATUS1,LOCATION|PARTNUM BERN|PRICEN,STATUSN,。。。
我不确定从哪里开始。。。。我应该使用嵌套查询吗?
您需要创建一个游标来循环遍历表。使用变量来控制表中的每一行是指同一产品还是指新产品。
类似这样的东西:
DECLARE @OLD_PRODUCT_ID int
set @OLD_PRODUCT_ID = -1
DECLARE MyCursor CURSOR FOR
select PRODUCT_ID, LOCATION, PARTNUMBER, PRICE, STATUS
FROM YourTable
OPEN MyCursor;
FETCH NEXT FROM MyCursor
INTO @PRODUCT_ID, @LOCATION, @PARTNUMBER, @PRICE, @STATUS --declare these variables
WHILE @@FETCH_STATUS = 0 BEGIN
if (@PRODUCT_ID = @OLD_PRODUCT_ID) begin
-- use the same line
end ele begin
-- new product = new line
end
@OLD_PRODUCT_ID = @PRODUCT_ID
FETCH NEXT FROM MyCursor
INTO @PRODUCT_ID, @LOCATION, @PARTNUMBER, @PRICE, @STATUS
END
CLOSE MyCursor;
DEALLOCATE MyCursor;
也有一些方法可以实现无循环,但sql更难。
位置列表是否有边界且很小?
如果是这样的话,你可以这样做:
select a.product_id ||
coalesce((select '|' || b.location || '|' || b.partnumber || '|' ||
b.price || '|' || trim(b.status) || ','
from session.products b
where b.location = '9999' and b.product_id = a.product_id), '') ||
coalesce((select '|' || c.location || '|' || c.partnumber || '|' ||
c.price || '|' || trim(c.status) || ','
from session.products c
where c.location = '8888' and c.product_id = a.product_id), '')
from (select distinct product_id as product_id from session.products) as a
您可以在其中为每个位置扩展语句。
对于sql中的一组无边界位置,有一些方法可以做到这一点,但读/写/调试并不容易,+Diego的游标解决方案可能更可取。
有趣的是,您可以递归地执行以下操作:
WITH Ordered_Data (product_id, orderIndex, dataString) as (
SELECT product_id, location, partnumber, price, status,
ROW_NUMBER() OVER(PARTITION_BY product_id ORDER BY product_id, location ASC),
product_id || '|' || location || '|' || partnumber || '|' ||
price || '|' || status
FROM Product_Location),
Combined_Data(product_id, orderIndex, dataString) as (
SELECT a.product_id, a.orderIndex, a.dataString
FROM Ordered_Data as a
JOIN (SELECT product_id, MAX(orderIndex) as orderIndex
FROM Ordered_Data
GROUP BY product_id) as b
ON b.product_id = a.product_id
AND b.orderIndex = a.orderIndex
UNION ALL
SELECT b.product_id, a.orderIndex, b.dataString || ',' || a.dataString
FROM Ordered_Data as a
JOIN Combined_Data as b
ON b.product_id = a.product_id
AND b.orderIndex - 1 = a.orderIndex)
SELECT dataString
FROM Combined_Data
WHERE orderIndex = 1
哪个产生预期:
9876543210|9999|3333|15.99|A,9876543210|4444|3333|14.99|A
1234567890|9999|5555|10.99|A,1234567890|8888|5555|11.99|A,1234567890|7777|5555|9.99|B
我不能保证会以多快的速度运行——特别是,你会想要一个超过(product_id
,location
)的索引(或类似的索引,并调整语句)。我相信DB2足够聪明,可以向后读取标记,所以方向应该不那么重要。
顺便说一句,我真的希望price
是numeric
或decimal
(精确小数),而不是float
或real
。