Retrieve column based on closest date - sql-server

Question

Thanks for your help in advance. I have an invoice table which is similar to below:
INV DATE | ITEM |SELL PRICE |COST PRICE
------------+-------+-----------+----------
30/06/2016 | DOOR1 |10 |5
The above item is sourced from the EU so I have another table (VEN_HIS) which lists a history of supplier prices for that item as below:
DATE |ITEM |CURRENCY |PRICE
------------+-------+-----------+------
17/05/2017 |DOOR1 |EUR |6
01/01/2017 |DOOR1 |EUR |5.8
29/05/2016 |DOOR1 |EUR |5.6
05/03/2016 |DOOR1 |EUR |5.5
What I want to do is join the tables to drop in the correct currency price we would have paid onto the invoice table as at the invoice date in other words the correct price is 5.6
This is my first post and I need to get some FX analysis done quickly so apologies for the formatting, any help would be greatly appreciated.

Answer 1

Its a simple question of Join and where clause.
create table #t1 (INV_DATE DATE,ITEM varchar(100), SELL_PRICE int, COST_PRICE int);
insert into #t1 values
('30/06/2016','DOOR1',10,5)
create table #ven_his (colDATE date, ITEM varchar(100), CURRENCY varchar(100),PRICE float);
insert into #ven_his values
('17/05/2017', 'DOOR1', 'EUR',6 ),
('01/01/2017', 'DOOR1', 'EUR',5.8),
('29/05/2016', 'DOOR1', 'EUR',5.6),
('05/03/2016', 'DOOR1', 'EUR',5.5)
SELECT top 1 a.INV_DATE, a.ITEM, b.CURRENCY, b.PRICE
FROM #t1 a
left join #ven_his b
on a.ITEM = b.ITEM
WHERE b.colDATE <=a.INV_DATE
ORDER BY b.colDATE DESC
output :
#t1
INV_DATE ITEM SELL_PRICE COST_PRICE
---------- ------ ----------- -----------
2016-06-30 DOOR1 10 5
#ven_his
colDATE ITEM CURRENCY PRICE
---------- --------- ------------ ------
2017-05-17 DOOR1 EUR 6
2017-01-01 DOOR1 EUR 5.8
2016-05-29 DOOR1 EUR 5.6
2016-03-05 DOOR1 EUR 5.5
INV_DATE ITEM CURRENCY PRICE
---------- --------- ----------- --------
2016-06-30 DOOR1 EUR 5.6

Answer 2

DECLARE #invoice table (INV_Date date, Item varchar(100),SellPrice numeric(5,2), Costprice numeric(5,2))
INSERT INTO #invoice
SELECT '20160630','DOOR1',10,5
SELECT * FrOm #invoice
DECLARE #ven_his table(Dates date,Item varchar(100),Currency varchar(10),Price numeric(5,2))
INSERT INTO #ven_his
SELECT '20170517','DOOR1','EUR',6
UNION ALL
SELECT '20170101','DOOR1','EUR',5.8
UNION ALL
SELECT '20160529','DOOR1','EUR',5.6
UNION ALL
SELECT '20160305','DOOR1','EUR',5.5
SELECT * FROM #ven_his
SELECT Top 1 i.Item,INV_Date,PRICE,Dates
FROM #invoice i
JOIN #ven_his v
ON i.Item = v.Item
ORDER BY ABS(DATEDIFF(DAY,i.INV_Date,v.Dates))

Answer 3

Use LEAD function to return the correct price for all items:
Create table #Invoice (INVDATE DATE, ITEM NVARCHAR(20), SELLPRICE SMALLMONEY, COSTPRICE SMALLMONEY)
INSERT #INVOICE VALUES ('2016-06-30', 'DOOR1', 10, 5)
--Test with additional invoices
--INSERT #INVOICE VALUES ('2017-02-22', 'DOOR1', 10, 5), ('2016-09-22', 'DOOR1', 10, 5)
CREATE TABLE #VENHIS ([DATE] DATE, ITEM NVARCHAR(20), CURRENCY NVARCHAR(5), PRICE SMALLMONEY)
INSERT #VENHIS VALUES ('2017-05-17', 'DOOR1', 'EUR', 6), ('2017-01-01', 'DOOR1', 'EUR', 5.8),('2016-05-29', 'DOOR1', 'EUR', 5.6), ('2016-03-05', 'DOOR1', 'EUR', 5.5)
SELECT I.*, V.PRICE
FROM #Invoice i
INNER JOIN (SELECT *, [DATE] as STARTDATE, LEAD([DATE]) OVER (PARTITION BY ITEM ORDER BY ITEM, [DATE] ASC) AS EndDate
FROM #VENHIS ) v ON i.ITEM=v.ITEM AND I.[INVDATE] BETWEEN V.STARTDATE AND DATEADD(D,-1,ISNULL(V.ENDDATE, '2099-01-01'))