Access Database Slow Finding Any Records Not Matching - ms-access

Question

My Access Database is slow when finding non-matching records
SELECT
RT3_Data_Query.Identifier, RT3_Data_Query.store, RT3_Data_Query.SOURCE,
RT3_Data_Query.TRAN_CODE, RT3_Data_Query.AMOUNT,
RT3_Data_Query.DB_CR_TYPE, RT3_Data_Query.status,
RT3_Data_Query.TRAN_DATE, RT3_Data_Query.ACCEPTED_DATE,
RT3_Data_Query.RECONCILED_DATE
FROM
RT3_Data_Query
LEFT JOIN Debit_AO_Query ON RT3_Data_Query.[Identifier] = Debit_AO_Query.[Identifier]
WHERE
(((Debit_AO_Query.Identifier) Is Null));
I'm doing a query of two queries I created. The last query is just to compare these two queries and show what is missing between them which is what i posted above. I'm matching an identifier between the two queries which looks like this 583005-01-20185804.33 which is a combination of store, date and amount.
Here is a link to the database:
https://wetransfer.com/downloads/15f912909fbe2ea0a5111e44b953d11a20190808195913/db9912

Answer 1

The query is slow because you don't use indexes on tables and join on concated fields (Identifier is Location & Date & Total)!
Each table needs a primary key or it is not a table! That should be an autonumber for the beginning!
Indexing:
Add a field called id to each table, datatype autonumber and make it PK.
Add a key for the fields compared in the join and the where clause (set all index properties (primary, unique, ignore) to no)!
for table RT3_Data (because it is huge create a copy first, then delete the data, or creating index will fail onMaxLocksPerFile):
store
AMOUNT
TRAN_DATE
after that reimport data from copy with query:
INSERT INTO RT3_DATA
SELECT [Copy Of RT3_DATA].*
FROM [Copy Of RT3_DATA];
for table Debit_AO:
Location
Total
Date (should be renamed as Date() is a VBA-Function)
Now change the queryRT3_Data_Query Without Matching Debit_AO_Queryto:
SELECT RT3_Data.store
,RT3_Data.SOURCE
,RT3_Data.TRAN_CODE
,RT3_Data.AMOUNT
,RT3_Data.DB_CR_TYPE
,RT3_Data.STATUS
,RT3_Data.TRAN_DATE
,RT3_Data.ACCEPTED_DATE
,RT3_Data.RECONCILED_DATE
FROM RT3_Data
LEFT JOIN Debit_AO
ON RT3_Data.[store] = Debit_AO.[Location]
AND RT3_Data.[AMOUNT] = Debit_AO.[Total]
AND RT3_Data.[TRAN_DATE] = Debit_AO.[DATE]
WHERE (
(
Debit_AO.Location IS NULL
AND Debit_AO.Total IS NULL
AND Debit_AO.[Date] IS NULL
)
);
Now the query executes in less than 10 seconds and for sure there are more optimizations (e.g composite index).