[AccessD] Fastest Way

Interesting problem here.

The quirk is going to be that last field.  Can you really have two
records with the first four fields (including a date and time) with
different 'Test Result Text'.  I would think you would end up with a
different value in the date and/or time fields for new test results.

So, ASSUMING that the Test Result is irrelevant to the uniqueness of a
record, I would recommend loading a collection with the first four
fields as the 'key' to each item in the collection.  I would create a
separate table with these 'keys' (for faster loading).  Put the fields
together with a delimiter like :.  This would create a one line string
with a unique identifier for each record.

For example, if the first record is 1, 1 , 1-29-2004,1214, you're ID
field would be 1:1:01292004:1214.  Adding that to a collection would put
all of the currently imported records into memory in a handy little tiny
string, that you can query with an 'error if it doesn't exist' function,
creating a pretty instantaneous check if a record has been imported.

However, if that fifth field can be different with the first four fields
the same, this would probably be a bad approach because that field could
jump the amount of memory being used quite a bit!

Drew

-----Original Message-----
From: accessd-bounces at databaseadvisors.com
[mailto:accessd-bounces at databaseadvisors.com] On Behalf Of Rocky Smolin
Sent: Thursday, January 14, 2010 9:01 AM
To: 'Access Developers discussion and problem solving'
Subject: [AccessD] Fastest Way

Dear List:

I have a medical database into which lab tests are imported from a
spreadsheet (exported from a mainframe medical records database at a big
hospital).  Front and back ends are Access 2003. The table
tblPatientTest has (in addition to the autonumber PK) 5 fields:

Patient ID (FK)

Test ID (FK)

Test Date as Date/Time (indexed duplicates OK)

Test Time as long integer - value between 0000 and 2399 (indexed
duplicates
OK)

Test Result - Text (indexed duplicates OK)

I'm using DAO to add the records to the table.  Imports will happen
monthly and the number of records will be on the order of 10,000-100,000
with mean probably around 20k-40k.

As the tests are imported I want to check the table to see if the test
record is already present by finding a record which matches all 5 fields
to prevent duplicate test records from being entered.

Since the import will take place monthly, import time is not super
critical but before importing the user will run an Error Report which
does all the error checking that the import does without actually doing
the import.  The user then resolves the errors and when the Error report
is clean, will run the import.  So the error report may have to be run
more than once to clean the data.

It is possible that the user will try to import a spreadsheet that has
already been imported. So it's important to screen for duplicates. 

So I want to find the fastest method of checking for duplicate.

The obvious thing is rs.FindFirst on all five fields, but I'm thinking
that may take a really long time.

Another possibility would be to create a temporary table in the front
end or external mdb, and create indexed records by concatenating all
five fields and checking for dups on that table.  Probably faster than
the first method but creating the table could take a lot of time when
the Patient Test table has a few hundred thousand records in it.

Or I could add the field of concatenated fields to the table itself as
the records are added, indexed and maintain that.

Or some other method that I haven't thought of or don't know about.

Any advice welcome.

MTIA

 

Rocky Smolin

Beach Access Software

858-259-4334

www.e-z-mrp.com <http://www.e-z-mrp.com/> 

www.bchacc.com <http://www.bchacc.com/> 

 

 

 

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