Selecting Historical Record Outside of Date Range - sql

Question

I have a situation where I need to select an address that was current for a particular date and time from an address history table. Some sample records might be as follows:
Address/Client JOIN Table (Address_Client_JOIN):
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|AddressId | ClientId |
-------------------------
|5 | 8888887 |
-------------------------
|6 | 8888887 |
-------------------------
History Table (Address_History):
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|HistoryId | AddressId | AddTypeId | StreetAddress | CreatedDate | ModifiedDate |
-------------------------------------------------------------------------------------------
|1 | 5 | 1 | 123 Home Street| 2013-03-11 21:08 | 2013-04-02 13:18|
-------------------------------------------------------------------------------------------
|2 | 5 | 2 | 456 My Avenue | 2013-03-11 21:08 | 2013-04-08 15:00|
-------------------------------------------------------------------------------------------
|3 | 6 | 1 | 789 Cat Road | 2013-05-17 12:00 | 2013-05-17 12:00|
-------------------------------------------------------------------------------------------
The requirements for this query are that I have to grab the earliest record where #dateOfService falls between the CreatedDate and the ModifiedDate and where the AddTypeId is "1", if there is one, otherwise any other AddTypeId. The query I've thus far created is:
SELECT TOP 1 ah.HistoryId, ah.AddTypeId, ah.AddressId, ah.StreetAddress,
ah.CreatedDate, ah.ModifiedDate
FROM Address_Client_JOIN acj WITH (NOLOCK)
INNER JOIN Address_History ah WITH (NOLOCK) ON ah.AddressId = acj.AddressId
WHERE apj.ClientId = #clientId
AND (ah.CreatedDate <= #dateOfService
AND (#dateOfService <= ah.ModifiedDate ))
ORDER BY
ah.HistoryId ASC, CASE WHEN ah.AddTypeId = 1 THEN 0 ELSE 1 END
This works fine as long as the #dateOfService falls between the CreatedDate and ModifiedDate. However, when I've got a #dateOfService that occurs after the ModifiedDate, I get nothing, obviously. I need to be able to account for a situation where (using the above data) #dateOfService is after the ModifiedDate of 5/17/2013. For example, where #dateOfService = '2013-08-01 12:30'.
Thanks in advance.

Answer 1

You are only selecting the top row. That means that you can move the where filter into the order by clause. Then, it becomes a priority rather than a filter.
So, if nothing matches the filter, you will still be able to get a row. I think the query you want is something like:
SELECT TOP 1 ah.HistoryId, ah.AddTypeId, ah.AddressId, ah.StreetAddress,
ah.CreatedDate, ah.ModifiedDate
FROM Address_Client_JOIN acj WITH (NOLOCK) INNER JOIN
Address_History ah WITH (NOLOCK)
ON ah.AddressId = acj.AddressId
WHERE apj.ClientId = #clientId
ORDER BY ah.HistoryId ASC,
(CASE WHEN ah.AddTypeId = 1 THEN 0 ELSE 1 END),
(case when ah.CreatedDate <= #dateOfService AND #dateOfService <= ah.ModifiedDate then 1
when #dateOfService > ah.ModifiedDate then 2
else 3
end)