I have three tables:
Fields
ID | FarmID | FIELD_NUM | Year
Farms
ID | ClientID
Clients
ID | CLIENT_NUM
I have a simple query to get CLIENT_NUM from the Clients table:
SELECT
(SELECT CLIENT_NUM FROM Clients
WHERE ID = (SELECT ClientID FROM Farms WHERE ID = FarmID)) AS CID
FROM Fields
WHERE Year = 2014 AND FIELD_NUM = '28-2'
In SQL Server, this works just fine; however, in Microsoft Access it takes forever. Is there a better way to run this query?
Instead of using sub-queries, try using JOIN
. Depending on how Access optimizes the query it could help with performance, but also it helps a lot with readability:
SELECT Clients.CLIENT_NUM as CID
FROM (Clients INNER JOIN Farms ON Clients.ID = Farms.ClientID)
INNER JOIN Fields ON Farms.ID = Fields.FarmID
WHERE Fields.Year = 2014 AND Fields.FIELD_NUM = '28-2'
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