SQL Update with AVG of Joined Tables - sql

Question

I'm trying to update the supplier lead time in a table by calculating the difference between date of order and stock receipt date....
UPDATE cr_accs
SET cr_accs.leadtime = Avg(Datediff(day, purchord_hdr.orderdate,
stock_trans.transdate))
FROM stock_items
INNER JOIN stock_trans
ON stock_trans.stockcode = stock_items.stockcode
INNER JOIN purchord_hdr
ON purchord_hdr.seqno = stock_trans.ref1
WHERE cr_accs.accno = purchord_hdr.accno
AND stock_trans.location = 1
AND stock_trans.ref2 = 'RECEIPT'
AND purchord_hdr.orderdate >= Dateadd(day, Datediff(day, 0, Getdate()),-730)
AND stock_items.isactive = 'Y'
AND stock_items.bincode NOT IN ( 'OIO', 'CON' )
However I'm getting an error
An aggregate may not appear in the set list of an UPDATE statement
I've seen other solutions where you would change the query to:
UPDATE cr_accs
SET cr_accs.leadtime = h.calc_lead_time
FROM (SELECT AVG(DATEDIFF(day, purchord_hdr.orderdate, stock_trans.transdate)) AS calc_lead_time
FROM stock_items
INNER JOIN stock_trans
ON stock_trans.stockcode = stock_items.stockcode
INNER JOIN purchord_hdr
ON purchord_hdr.seqno = stock_trans.ref1
INNER JOIN cr_accs
ON cr_accs.accno = purchord_hdr.accno
WHERE cr_accs.accno = purchord_hdr.accno
AND stock_trans.location = 1
AND stock_trans.ref2 = 'RECEIPT'
AND purchord_hdr.orderdate >= Dateadd(day, Datediff(day, 0, Getdate()),-730)
AND stock_items.isactive = 'Y'
AND stock_items.bincode NOT IN ( 'OIO', 'CON' ) ) h
However this is not the solution for me as it doesn't define that the lead time is unique to each supplier...
It may be helpful to point out that each supplier is identified by cr_accs.accno
Any ideas please?

Answer 1

You can also do what you want using a correlated subquery, which might be what you were trying to do:
UPDATE cr_accs
SET cr_accs.leadtime =
(SELECT AVG(DATEDIFF(day, p.orderdate, st.transdate)) AS calc_lead_time
FROM stock_items si JOIN
stock_trans st
ON st.stockcode = si.stockcode JOIN
purchord_hdr p
ON p.seqno = st.ref1
WHERE cr_accs.accno = p.accno AND
st.location = 1 AND
st.ref2 = 'RECEIPT' AND
p.orderdate >= Dateadd(day, Datediff(day, 0, Getdate()), -730) AND
si.isactive = 'Y' AND
si.bincode NOT IN ( 'OIO', 'CON' )
);
I introduced table aliases so the query is easier to write and to read.
SQL Server also gives you the ability to express this using APPLY:
UPDATE a
SET a.leadtime = p.calc_lead_time
FROM cr_accs a CROSS APPLY
(SELECT AVG(DATEDIFF(day, p.orderdate, st.transdate)) AS calc_lead_time
FROM stock_items si JOIN
stock_trans st
ON st.stockcode = si.stockcode JOIN
purchord_hdr p
ON p.seqno = st.ref1
WHERE a.accno = p.accno AND
st.location = 1 AND
st.ref2 = 'RECEIPT' AND
p.orderdate >= Dateadd(day, Datediff(day, 0, Getdate()), -730) AND
si.isactive = 'Y' AND
si.bincode NOT IN ( 'OIO', 'CON' )
) p;

Answer 2

Try this join of the table to the query:
UPDATE c
SET c.leadtime = h.calc_lead_time
FROM cr_accs c
INNER JOIN (
SELECT purchord_hdr.accno,
AVG(DATEDIFF(day, purchord_hdr.orderdate, stock_trans.transdate)) AS calc_lead_time
FROM stock_items
INNER JOIN stock_trans ON stock_trans.stockcode = stock_items.stockcode
INNER JOIN purchord_hdr ON purchord_hdr.seqno = stock_trans.ref1
WHERE stock_trans.location = 1
AND stock_trans.ref2 = 'RECEIPT'
AND purchord_hdr.orderdate >= Dateadd(day, Datediff(day, 0, Getdate()),-730)
AND stock_items.isactive = 'Y'
AND stock_items.bincode NOT IN ('OIO', 'CON')
GROUP BY purchord_hdr.accno
) h ON h.accno = c.accno
I assume (by your code and the error message) that you are using SQL Server.