How do I remove duplicate results by looking for max date? - sql

Question

I know I have duplicate results from this query because the tables ReleaseHistory and IterationHistory have multiple records per ReleaseID and IterationID. I would like to only select the records with max date from dbo.ReleaseHistory and dbo.IterationHistory. How would I do that in this query? SQL SERVER 2008
SELECT dbo.Assignable.AssignableID AS ID,
dbo.EntityType.Abbreviation AS Entity,
dbo.General.Name, dbo.Assignable.Effort,
dbo.Assignable.EffortCompleted,
dbo.Assignable.EffortToDo,
dbo.EntityState.Name AS State,
dbo.ReleaseHistory.Name AS Release,
dbo.IterationHistory.Name AS Iteration,
dbo.General.CustomField3 AS [Scrum Team]
FROM dbo.Assignable INNER JOIN
dbo.General ON dbo.Assignable.AssignableID =
dbo.General.GeneralID INNER JOIN
dbo.EntityType ON dbo.General.EntityTypeID =
dbo.EntityType.EntityTypeID INNER JOIN
dbo.EntityState ON dbo.Assignable.EntityStateID =
dbo.EntityState.EntityStateID AND
dbo.EntityType.EntityTypeID =
dbo.EntityState.EntityTypeID INNER JOIN
dbo.ReleaseHistory ON dbo.Assignable.ReleaseID =
dbo.ReleaseHistory.ReleaseID INNER JOIN
dbo.IterationHistory ON
dbo.Assignable.IterationID =
dbo.IterationHistory.IterationID LEFT OUTER JOIN
dbo.CustomField ON dbo.General.CustomField3 =
dbo.CustomField.CustomFieldID
WHERE (dbo.Assignable.ProjectID = 4054)
GROUP BY dbo.Assignable.AssignableID,
dbo.EntityType.Abbreviation,
dbo.General.Name,
dbo.Assignable.Effort,
dbo.Assignable.EffortCompleted,
dbo.Assignable.EffortToDo,
dbo.EntityState.Name,
dbo.ReleaseHistory.Name,
dbo.IterationHistory.Name,
dbo.General.CustomField3

Answer 1

Brian,
I am amusing you are doing this in MS SQL and there will always be at least one record in ReleaseHistory and IterationHistory tables. If assumptions are correct then you can simply use CROSS APPLY to get top 1 record from both tables.
SELECT
dbo.Assignable.AssignableID AS ID ,
dbo.EntityType.Abbreviation AS Entity ,
dbo.General.Name ,
dbo.Assignable.Effort ,
dbo.Assignable.EffortCompleted ,
dbo.Assignable.EffortToDo ,
dbo.EntityState.Name AS State ,
Release ,
Iteration ,
dbo.General.CustomField3 AS [Scrum Team]
FROM
dbo.Assignable
INNER JOIN dbo.General ON dbo.Assignable.AssignableID = dbo.General.GeneralID
INNER JOIN dbo.EntityType ON dbo.General.EntityTypeID = dbo.EntityType.EntityTypeID
INNER JOIN dbo.EntityState ON dbo.Assignable.EntityStateID = dbo.EntityState.EntityStateID
AND dbo.EntityType.EntityTypeID = dbo.EntityState.EntityTypeID
CROSS APPLY( SELECT TOP 1 name Release FROM ReleaseHistory WHERE ReleaseID = Assignable.ReleaseID ORDER BY MaxDateColumn) a
CROSS APPLY( SELECT TOP 1 name Iteration FROM IterationHistory WHERE IterationID = Assignable.IterationID ORDER BY MaxDateColumn) b
LEFT OUTER JOIN dbo.CustomField ON dbo.General.CustomField3 = dbo.CustomField.CustomFieldID
WHERE
( dbo.Assignable.ProjectID = 4054 )
GROUP BY
dbo.Assignable.AssignableID ,
dbo.EntityType.Abbreviation ,
dbo.General.Name ,
dbo.Assignable.Effort ,
dbo.Assignable.EffortCompleted ,
dbo.Assignable.EffortToDo ,
dbo.EntityState.Name ,
dbo.ReleaseHistory.Name ,
dbo.IterationHistory.Name ,
dbo.General.CustomField3