petekipe
asked on
Update table A from TOP in table B
Given table A as follows:
pk_a expiration_date
1 1/15/2012
2 1/15/2012
3 2/12/2012
and table B as follows:
pk_b fk_a date_expires
1 1 1/15/2012
2 1 1/15/2013
3 2 1/15/2012
4 2 1/15/2013
5 3 2/12/2011
6 3 2/12/2012
7 3 2/12/2013
How can I write an update query in Access 2003 SQL that will update A.expiration_date with B.date_expires from the highest B.pk_b for the join between A.pk_a and B.fk_a?
Thanks in advance,
Pete
pk_a expiration_date
1 1/15/2012
2 1/15/2012
3 2/12/2012
and table B as follows:
pk_b fk_a date_expires
1 1 1/15/2012
2 1 1/15/2013
3 2 1/15/2012
4 2 1/15/2013
5 3 2/12/2011
6 3 2/12/2012
7 3 2/12/2013
How can I write an update query in Access 2003 SQL that will update A.expiration_date with B.date_expires from the highest B.pk_b for the join between A.pk_a and B.fk_a?
Thanks in advance,
Pete
ASKER
Max function is my problem -- I don't know how to incorporate it. Can you provide an example?
Update A set A.expiration_date = Dmax("expiration_date", "B", "fk_a=" & pk_a)
The above assumes pk_a is numeric.
If it is text then you would need..
Update A set A.expiration_date = Dmax("expiration_date", "B", "fk_a='" & pk_a "'")
You cannot run an update query in Access if it includes any simple aggregate function (max(), min() , avg() etc) anywher in its structure.
You CAN use the domain aggregates DMax() DMin() etc as in the solution above.
The above assumes pk_a is numeric.
If it is text then you would need..
Update A set A.expiration_date = Dmax("expiration_date", "B", "fk_a='" & pk_a "'")
You cannot run an update query in Access if it includes any simple aggregate function (max(), min() , avg() etc) anywher in its structure.
You CAN use the domain aggregates DMax() DMin() etc as in the solution above.
ASKER
Neither of the solutions in the stackoverflow link work in Access 2003, nor does the solution in access-programmers.co.uk. The following looks logically like what I want -- I've changed the code to the real table and column names:
UPDATE Station A
SET expiration_date =
(SELECT MAX([date_expires])
FROM License B
WHERE A.pk_station = B.fk_station)
But I'm getting the error, "Operation must use an updateable query." Any ideas?
UPDATE Station A
SET expiration_date =
(SELECT MAX([date_expires])
FROM License B
WHERE A.pk_station = B.fk_station)
But I'm getting the error, "Operation must use an updateable query." Any ideas?
See my post immediately before yours.
ASKER
peter57r, you're really close -- but the code sets Station.expiration_date to the maximum expiration date of any of its joined rows from License. Referring to the tables given in my original post, I need to set A.expiration_date to the B.date_expires of the highest B.pk_b for the join of A.pk_a = B.fk_a. i.e, the date I want isn't necessarily the maximum date in B for the join, it should be the last-entered date (having the highest B.pk_b for the join). Does that make sense?
The code I posted does what you are asking.
Post the sql you are using.
Post the sql you are using.
ASKER
UPDATE Station
SET Station.expiration_date = Dmax("date_expires", "License", "fk_station=" & pk_station)
What in the code causes date_expires to be chosen from the highest License pk related by foreign key to a particular Station pk?
SET Station.expiration_date = Dmax("date_expires", "License", "fk_station=" & pk_station)
What in the code causes date_expires to be chosen from the highest License pk related by foreign key to a particular Station pk?
This bit of the DMax does the matching...
"fk_station=" & pk_station)
This Update command definitely updates table Station with the max date_expires for the matching keys.
Can you confirm that both Station.expiration_date and date_expires are defined as datetime fields.
"fk_station=" & pk_station)
This Update command definitely updates table Station with the max date_expires for the matching keys.
Can you confirm that both Station.expiration_date and date_expires are defined as datetime fields.
Your Query:
UPDATE Station A
SET expiration_date =
(SELECT MAX([date_expires])
FROM License B
WHERE A.pk_station = B.fk_station)
First option: Run the sub query individually and check whether its giving records or not.
SELECT MAX([date_expires]) FROM License B WHERE A.pk_station = B.fk_station
if you still face the error check there might be null values inside "date_expires" field
if it contains null or blank values filter null value records by using
SELECT MAX([date_expires]) FROM License B WHERE A.pk_station = B.fk_station and isnull([date_expires],'') <>''
UPDATE Station A
SET expiration_date =
(SELECT MAX([date_expires])
FROM License B
WHERE A.pk_station = B.fk_station)
First option: Run the sub query individually and check whether its giving records or not.
SELECT MAX([date_expires]) FROM License B WHERE A.pk_station = B.fk_station
if you still face the error check there might be null values inside "date_expires" field
if it contains null or blank values filter null value records by using
SELECT MAX([date_expires]) FROM License B WHERE A.pk_station = B.fk_station and isnull([date_expires],'') <>''
ASKER
keyu: Access 2003 does not allow an update query to contain a subquery containing a MAX or TOP function.
peter57r: Both fields are defined as datetime fields. I don't think I made the point clear in my ID: 37815355 post: I don't want the maximum date value -- I want the date value from the most recent License row, which is the row having the highest pk_license among the joined rows.
peter57r: Both fields are defined as datetime fields. I don't think I made the point clear in my ID: 37815355 post: I don't want the maximum date value -- I want the date value from the most recent License row, which is the row having the highest pk_license among the joined rows.
ASKER CERTIFIED SOLUTION
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UPDATE Station A
SET expiration_date =
(SELECT top 1 date_expires
FROM License B
WHERE A.pk_station = B.fk_station order by date_expires desc)
SET expiration_date =
(SELECT top 1 date_expires
FROM License B
WHERE A.pk_station = B.fk_station order by date_expires desc)
ASKER
peter57r: Bingo! For the record, following is my final query:
Update Station
SET Station.expiration_date = DLookup("date_expires", "License", "pk_license =" & Dmax("pk_license", "License", "fk_station= " & pk_station))
Note: Out of roughly 18000 Station rows, only about 1000 had corresponding License rows. According to MS's docs on DLookup/Dmax, if the conditions are not met, null is returned, which caused 17000 rows not to be updated because of type conversion errors. Ideally, the update could have been accomplished via a right join, to eliminate unlicensed stations from even being considered, but as was pointed out early in this thread, Access doesn't allow an aggregation function in an update query.
Thank you VERY much for your insightful help, peter57r!
Pete
Update Station
SET Station.expiration_date = DLookup("date_expires", "License", "pk_license =" & Dmax("pk_license", "License", "fk_station= " & pk_station))
Note: Out of roughly 18000 Station rows, only about 1000 had corresponding License rows. According to MS's docs on DLookup/Dmax, if the conditions are not met, null is returned, which caused 17000 rows not to be updated because of type conversion errors. Ideally, the update could have been accomplished via a right join, to eliminate unlicensed stations from even being considered, but as was pointed out early in this thread, Access doesn't allow an aggregation function in an update query.
Thank you VERY much for your insightful help, peter57r!
Pete
use the max functionfor getting highest value