delete records from one table if not in another

[mcnewsxp]

how can i delete records from one table if the records do not exist in a
matching table? i am making a backup of a table before an import is
performed. the users may need to undo the backup so i need to be able to
delete only the new records. this is not working, but you get the idea:

DELETE tblPatient.* FROM tblPatient INNER JOIN tblPatientBackup ON
tblPatient.PatientID = tblPatientBackup.PatientID
WHERE tblPatient.PatientID <> tblPatientBackup.PatientID;

tia,
mcnewxp

 

[mcnewsxp]

Try creating an unmatched query and changing it to a delete query. There's
a wixard for creating an unmatched query by going to queries in the
database window and clicking new.

good idea.
except when i do this no fields show up in the list....???

 

[John Spencer]

Well, if you have imported then into tblPatient then they are in the table.
So an unmatched query is not going to show you anything.

STEP 1: BACKUP your data before attempting the following.
STEP 2: BACKUP your data before attempting the following.

Without a backup you cannot restore the data if this does not work the way you
expect. Here are four options - choose your favorite

Option 1:
DELETE
FROM TblPatient
WHERE tblPatient.PatientID in
(SELECT PatientID FROM ImportSourceTable)

Option 2: Optionally if you want to use the backup table instead of the import
table.
DELETE
FROM tblPatient
WHERE tblPatient.PatientID IN
(SELECT Temp.PatientID
FROM tblPatient as TEMP LEFT JOIN tblPatient_BU
ON Temp.PatientID = tblPatient_BU.PatientID
WHERE TblPatient_BU.PatientID is NULL)

Option 3:
On the other hand, you might just be able to replace TblPatient with
TblPatient_BU. Unless other changes have been made to the records you want to
retain, this would seem to be the easiest solution.

Option 4:
Another option would be to add a date field (DateCreated) to tblPatient and
set its default to NOW(). Then all you have to do is identify records that
were created at a certain date and time and delete them.

DELETE
FROM tblPatient
WHERE DateCreated Between #2008-12-18 13:59:00# and #2008-12-18 14:00:00#

John Spencer
Access MVP 2002-2005, 2007-2008
The Hilltop Institute
University of Maryland Baltimore County

 

[mcnewsxp]

Well, if you have imported then into tblPatient then they are in the
table. So an unmatched query is not going to show you anything.

STEP 1: BACKUP your data before attempting the following.
STEP 2: BACKUP your data before attempting the following.

Without a backup you cannot restore the data if this does not work the way
you expect. Here are four options - choose your favorite

Option 1:
DELETE
FROM TblPatient
WHERE tblPatient.PatientID in
(SELECT PatientID FROM ImportSourceTable)

Option 2: Optionally if you want to use the backup table instead of the
import table.
DELETE
FROM tblPatient
WHERE tblPatient.PatientID IN
(SELECT Temp.PatientID
FROM tblPatient as TEMP LEFT JOIN tblPatient_BU
ON Temp.PatientID = tblPatient_BU.PatientID
WHERE TblPatient_BU.PatientID is NULL)

Option 3:
On the other hand, you might just be able to replace TblPatient with
TblPatient_BU. Unless other changes have been made to the records you want
to retain, this would seem to be the easiest solution.

Option 4:
Another option would be to add a date field (DateCreated) to tblPatient
and set its default to NOW(). Then all you have to do is identify records
that were created at a certain date and time and delete them.

DELETE
FROM tblPatient
WHERE DateCreated Between #2008-12-18 13:59:00# and #2008-12-18 14:00:00#

the date idea is a good one.
i tried the replace but i couldn't delete the original records due to
dependancies.

 

[mcnewsxp]

If you make a backup of the original table and then import new records
into the backup table, the new records will not be in the original table.
Your unmatched query should look at the backup table to find records that
are not in the original table. If you do not return any records, are you
specifying an appropriate field in the unmatched query?

I am a bit puzzeled by your response "....no fields show up in the
list...." By "fields" do you mean records or do you truly mean fields?
Please clarify.

when i go to create the unmatched query after selecting the two tables - on
the form where you select the fields to match theres nothing in the
lists...?

 

[mcnewsxp]

Are you talking about the wizard and the two listboxes for selecting
fields to match?

yes

 

[mcnews]

1.    When you go to New - Unmatched Query to start the wizard, do you get a
listbox with all your tables?

2.    You need to select the Backup table first and then the originaltable.
Then do you get two listboxes where the left listbox shows the fields in the
backup table and the right list box shows the fields in the original table?

Steve

i tried it on my work PC and it works fine.....

 

[mcnews]

Well, if you have imported then into tblPatient then they are in the table.
So an unmatched query is not going to show you anything.

STEP 1:  BACKUP your data before attempting the following.
STEP 2:  BACKUP your data before attempting the following.

Without a backup you cannot restore the data if this does not work the way you
expect.  Here are four options - choose your favorite

Option 1:
DELETE
FROM TblPatient
WHERE tblPatient.PatientID in
(SELECT PatientID FROM ImportSourceTable)

Option 2: Optionally if you want to use the backup table instead of the import
table.
DELETE
FROM tblPatient
WHERE tblPatient.PatientID IN
   (SELECT Temp.PatientID
    FROM tblPatient as TEMP LEFT JOIN tblPatient_BU
    ON Temp.PatientID = tblPatient_BU.PatientID
    WHERE TblPatient_BU.PatientID is NULL)

Option 3:
On the other hand, you might just be able to replace TblPatient with
TblPatient_BU. Unless other changes have been made to the records you want to
retain, this would seem to be the easiest solution.

Option 4:
Another option would be to add a date field (DateCreated) to tblPatient and
set its default to NOW().  Then all you have to do is identify records that
were created at a certain date and time and delete them.

DELETE
FROM tblPatient
WHERE DateCreated Between #2008-12-18 13:59:00# and #2008-12-18 14:00:00#

John Spencer
Access MVP 2002-2005, 2007-2008
The Hilltop Institute
University of Maryland Baltimore County

your 3rd option is one that i tried, but i couldn't delete the
tblPatient records because of foreignkey violations.

 

[John Spencer]

Well, if the data in tblPatient is linked to other tables then you will have to
go into the relationships window
, delete the relationship links involving tblPatient
, save the changes
, then replace (or rename) tblPatient with tblPatient_BU. (I suggest you
rename tblPatient to tblPatient_Original and tblPatient_BU to tblPatient)
, and then re-establish the relationships.

Test things and if all seems to be working correctly, you can then rename
tblPatient_Original to tblPatient_BU or delete tblPatient_Original.


John Spencer
Access MVP 2002-2005, 2007-2008
The Hilltop Institute
University of Maryland Baltimore County

 

[mcnews]

Is your problem solved then?

Steve





i tried it on my work PC and it works fine.....

i'll have to try it again at home this evening, but i can move on with
my work PC.
thanks.