MS Access SQL - How do I fix my Joins? - sql

Question

I'm not familiar with MS Access 2003-2007 SQL, but I have to maintain/extend a project that uses it. (The original author has left the company. Hooray for legacy code.) What I'm trying to do is join a number of related tables so that the query gives me the number of transactions for a particular user within a particular time range. The end result of this is that I want to see how many hours passed between an OUT event and the previous IN event for that user.
The code I have so far is as follows:
SELECT Directions.DirectionText, Transactions.Timestamp
FROM Users
LEFT JOIN AccessNumbers ON Users.AccessNumberID = AccessNumbers.AccessNumberID
LEFT JOIN Transactions ON AccessNumbers.Number = Transactions.Number
LEFT JOIN Events ON Transactions.Event = Events.EventNumber
LEFT JOIN Readers ON Transactions.ReaderID = Readers.ReaderID
LEFT JOIN Directions ON Readers.Direction = Direction.Direction
WHERE
(Events.EventNum IN (1, 22)) AND
(Users.[Name] = "firstName") AND
(Users.Surname = "Surname") AND
(Transactions.Timestamp >=#2017-04-10 01:00:00#) AND
(Transactions.Timestamp <=#2017-05-09 14:57:30#)
ORDER BY Transactions.Timestamp
The error I receive is "Syntax Error (missing operator in query expression 'Users.AccessNumberID = ... Direction.Direction'
I have also tried the following, to receive "Syntax Error on JOIN operation':
SELECT Directions.DirectionText, Transactions.Timestamp
FROM Users
LEFT JOIN (AccessNumbers ON Users.AccessNumberID =
AccessNumbers.AccessNumberID)
ON (AccessNumbers.Number = Transactions.Number)
ON (Transactions.Event = Events.EventNumber)
ON (Transactions.ReaderID = Readers.ReaderID)
ON (Readers.Direction = Direction.Direction)
WHERE ...
I'm aware that the SQL needs parentheses, but I don't know where to place them.

Answer 1

I've had issues with Access trying to put in my parentheses for me in the past... especially with LEFT joins. I'd normally parenthesize your first query like so:
SELECT Directions.DirectionText, Transactions.Timestamp
FROM ((((Users
LEFT JOIN AccessNumbers ON Users.AccessNumberID = AccessNumbers.AccessNumberID)
LEFT JOIN Transactions ON AccessNumbers.Number = Transactions.Number)
LEFT JOIN Events ON Transactions.Event = Events.EventNumber)
LEFT JOIN Readers ON Transactions.ReaderID = Readers.ReaderID)
LEFT JOIN Directions ON Readers.Direction = Directions.Direction
WHERE
(Events.EventNum IN (1, 22)) AND
(Users.[Name] = "firstName") AND
(Users.Surname = "Surname") AND
(Transactions.Timestamp >=#2017-04-10 01:00:00#) AND
(Transactions.Timestamp <=#2017-05-09 14:57:30#)
ORDER BY Transactions.Timestamp
Your second query would need more LEFT JOIN clauses thrown in to function.

Answer 2

A simple trick is the following:
Add a closing parenthesis before each LEFT beyond the first.
Add an opening parenthesis after FROM for each LEFT beyond the first.
Result:
SELECT Directions.DirectionText, Transactions.Timestamp
FROM ((((Users
LEFT JOIN AccessNumbers ON Users.AccessNumberID = AccessNumbers.AccessNumberID
) LEFT JOIN Transactions ON AccessNumbers.Number = Transactions.Number
) LEFT JOIN Events ON Transactions.Event = Events.EventNumber
) LEFT JOIN Readers ON Transactions.ReaderID = Readers.ReaderID
) LEFT JOIN Directions ON Readers.Direction = Direction.Direction
WHERE
(Events.EventNum IN (1, 22)) AND
(Users.[Name] = "firstName") AND
(Users.Surname = "Surname") AND
(Transactions.Timestamp >=#2017-04-10 01:00:00#) AND
(Transactions.Timestamp <=#2017-05-09 14:57:30#)
ORDER BY Transactions.Timestamp
The result is the same as Sturgus says, but adding them this way makes sense to me. For layout purposes, you might move each closing parenthesis to the line above it.