Tough SQL Rank query - sql-server

Question

Scenario: primary user table plus a separate audit table that tracks changes to the user's name. Each time a user is added or part of their name is edited, we write a row to the audit table.
Trying to write a query that pulls the most immediate former name
select nsh.AuthEmail, nsh.UserID, nsh.name_lastnamefirst, t.FormerName, t.RankOrder
from (
Select
an.AuditNameID, nsh.AuthEmail, nsh.UserID, nsh.name_lastnamefirst,
FormerName = CASE WHEN RTRIM(an.LastName) <> RTRIM(nsh.LastName) OR RTRIM(an.FirstName) <> RTRIM(nsh.FirstName) OR RTRIM(an.Suffix) <> RTRIM(nsh.Suffix) OR RTRIM(an.MaidenName)<>RTRIM(nsh.MaidenName) THEN LTRIM(an.LastName + ' ' + an.Suffix + ', ' + an.FirstName + ' ' + ISNULL(an.MiddleName,''))
ELSE null
END,
RANK() over (partition by an.UserID order by an.AuditNameID DESC) RankOrder
From [dbo].[AuditName] an
INNER JOIN dbo.StudentPrograms p ON an.UserID = p.UserID
INNER JOIN dbo.NameScalarHelper nsh ON p.UserID = nsh.UserID
WHERE p.SiteProgramID = 139 AND p.IsActive =1
) t
RIGHT OUTER JOIN dbo.NameScalarHelper nsh ON nsh.UserID = t.UserID
where FormerName is not null
The problem is that I can't figure out how to return the data from audit table where the RANK is RANK -1 because the top rank is the current data. Let me know if any ideas.

Answer 1

Looking at your requirement you basicly need to return latest name that doesn't match current one from your Audit table.
I think you could use OUTER APPLY to achieve that:
SELECT *
FROM [dbo].[StudentPrograms] AS SP
INNER JOIN [dbo].[NameScalarHelper] AS NSH
ON NSH.UserID = SP.UserID
OUTER APPLY (
SELECT TOP (1) *
FROM [dbo].[AuditName] AS AN
WHERE AN.UserID = SP.UserID
AND (
RTRIM(AN.LastName) <> RTRIM(NSH.LastName)
OR RTRIM(AN.FirstName) <> RTRIM(NSH.FirstName)
OR RTRIM(AN.Suffix) <> RTRIM(NSH.Suffix)
OR RTRIM(AN.MaidenName) <> RTRIM(NSH.MaidenName)
)
ORDER BY AuditNameID DESC
) AS AN
WHERE SP.SiteProgramID = 139
AND SP.IsActive = 1;
This will find latest name from your audit table which doesn't match latest one.
By the way, I'd strongly suggest to clean up your database and remove any trailing/leading spaces, so that you don't need to use LTRIM() or RTRIM() in your where clause so that SQL Server would be able to make use of indexes. Read this article for more details.
SELECT *
FROM [dbo].[StudentPrograms] AS SP
INNER JOIN [dbo].[NameScalarHelper] AS NSH
ON NSH.UserID = SP.UserID
OUTER APPLY (
SELECT TOP (1) *
FROM [dbo].[AuditName] AS AN
WHERE AN.UserID = SP.UserID
AND (
AN.LastName <> NSH.LastName
OR AN.FirstName <> NSH.FirstName
OR AN.Suffix <> NSH.Suffix
OR AN.MaidenNam) <> NSH.MaidenName
)
ORDER BY AuditNameID DESC
) AS AN
WHERE SP.SiteProgramID = 139
AND SP.IsActive = 1;
I was trying to understand the way you store data and replicated a tiny example:
DECLARE #User TABLE
(
UserID INT
, FirstName VARCHAR(50)
, LastName VARCHAR(50)
);
DECLARE #Audit TABLE
(
AuditID INT IDENTITY(1, 1)
, UserID INT
, FirstName VARCHAR(50)
, LastName VARCHAR(50)
);
INSERT INTO #User (UserID, FirstName, LastName)
VALUES (1, 'Ben', 'White');
INSERT INTO #Audit (UserID, FirstName, LastName)
VALUES (1, 'Ben', 'White');
SELECT *
FROM #User AS U
OUTER APPLY (
SELECT TOP (1) *
FROM #Audit AS A
WHERE A.UserID = U.UserID
AND (
A.FirstName <> U.FirstName
OR A.LastName <> U.LastName
)
ORDER BY A.AuditID DESC
) AS A;
UPDATE U
SET U.LastName = 'Whiter'
FROM #User AS U
WHERE U.UserID = 1;
INSERT INTO #Audit (UserID, FirstName, LastName)
VALUES (1, 'Ben', 'Whiter');
SELECT *
FROM #User AS U
OUTER APPLY (
SELECT TOP (1) *
FROM #Audit AS A
WHERE A.UserID = U.UserID
AND (
A.FirstName <> U.FirstName
OR A.LastName <> U.LastName
)
ORDER BY A.AuditID DESC
) AS A;
UPDATE U
SET U.LastName = 'Whitest'
FROM #User AS U
WHERE U.UserID = 1;
INSERT INTO #Audit (UserID, FirstName, LastName)
VALUES (1, 'Ben', 'Whitest');
SELECT *
FROM #User AS U
OUTER APPLY (
SELECT TOP (1) *
FROM #Audit AS A
WHERE A.UserID = U.UserID
AND (
A.FirstName <> U.FirstName
OR A.LastName <> U.LastName
)
ORDER BY A.AuditID DESC
) AS A;
INSERT INTO #User (UserID, FirstName, LastName)
VALUES (2, 'Tom', 'Brooks');
INSERT INTO #Audit (UserID, FirstName, LastName)
VALUES (2, 'Tom', 'Brooks');
SELECT *
FROM #User AS U
OUTER APPLY (
SELECT TOP (1) *
FROM #Audit AS A
WHERE A.UserID = U.UserID
AND (
A.FirstName <> U.FirstName
OR A.LastName <> U.LastName
)
ORDER BY A.AuditID DESC
) AS A;
I assumed that when you create a user - you also add record to Audit table for consistency. Each time you make an update - you also log that into Audit table. Finally I just added yet another user and ran the query.
That's the output for each query:
User was created:
UserID FirstName LastName AuditID UserID FirstName LastName
------ --------- -------- ------- ------ --------- --------
1 Ben White null null null null
Its' last name was changed first time:
UserID FirstName LastName AuditID UserID FirstName LastName
------ --------- -------- ------- ------ --------- --------
1 Ben Whiter 1 1 Ben White
Its' last name was changed second time:
UserID FirstName LastName AuditID UserID FirstName LastName
------ --------- -------- ------- ------ --------- --------
1 Ben Whitest 2 1 Ben Whiter
A new user has been added:
UserID FirstName LastName AuditID UserID FirstName LastName
------ --------- -------- ------- ------ --------- --------
1 Ben Whitest 2 1 Ben Whiter
2 Tom Brooks null null null null
Everything else is just formatting and you should not do that in SQL Server - this should be done in application layer.

Answer 2

By looking at your query, I'm guessing you are getting back all of a person's past names, since you have no filter based on the RankOrder that you've created. Your current name should be 1 in the RankOrder, I assume, and so your most recent previous name would be ranked 2. You can add this to your derived table's where clause like this:
select nsh.AuthEmail, nsh.UserID, nsh.name_lastnamefirst, t.FormerName, t.RankOrder
from (
Select
an.AuditNameID, nsh.AuthEmail, nsh.UserID, nsh.name_lastnamefirst,
FormerName = CASE WHEN RTRIM(an.LastName) <> RTRIM(nsh.LastName) OR RTRIM(an.FirstName) <> RTRIM(nsh.FirstName) OR RTRIM(an.Suffix) <> RTRIM(nsh.Suffix) OR RTRIM(an.MaidenName)<>RTRIM(nsh.MaidenName) THEN LTRIM(an.LastName + ' ' + an.Suffix + ', ' + an.FirstName + ' ' + ISNULL(an.MiddleName,''))
ELSE null
END,
RANK() over (partition by an.UserID order by an.AuditNameID DESC) RankOrder
From [dbo].[AuditName] an
INNER JOIN dbo.StudentPrograms p ON an.UserID = p.UserID
INNER JOIN dbo.NameScalarHelper nsh ON p.UserID = nsh.UserID
WHERE p.SiteProgramID = 139 AND p.IsActive =1 and RankOrder = 2
) t
RIGHT OUTER JOIN dbo.NameScalarHelper nsh ON nsh.UserID = t.UserID
where FormerName is not null
Let me know if I am missing something.