alternative to sub query in join - sql-server

Question

I have a SQL query that I'm trying to optimize.
Is there a better way to avoid using subquery here?
Got a suggestion on using Row_number(),
posting this with some corrections
DECLARE #curdate DATETIME
SET #curdate = GETDATE()
SELECT DISTINCT
SIS.StudentID, StudentCoverage.StudentCoverageDataID,
Student.FirstName, Student.LastName,
Student.DateOfBirth, Student.Gender,
ASMT.AssessmentDate
FROM
SIS (NOLOCK)
INNER JOIN
SISMaster (NOLOCK) ON SISMaster.SISID = SIS.SISID
INNER JOIN
Assessment ASMT ON SIS.StudentID = ASMT.StudentId
INNER JOIN
StudentCoverage (NOLOCK) ON StudentCoverage.StudentID = SIS.StudentID
INNER JOIN
Organization (NOLOCK) ON StudentCoverage.OrgID = Organization.OrganizationID
INNER JOIN
Student (NOLOCK) ON Student.StudentID = SIS.StudentID
INNER JOIN
StudentCoverageData (NOLOCK) ON StudentCoverageData.StudentCoverageID = StudentCoverage.StudentCoverageID
AND StudentCoverageData.StudentCoverageDataID = (SELECT TOP 1 StudentCoverageData.StudentCoverageDataID
FROM StudentCoverage
INNER JOIN StudentCoverageData ON StudentCoverageData.StudentCoverageID = StudentCoverage.StudentCoverageID
WHERE StudentCoverage.StudentId = SIS.StudentID
AND StudentCoverageData.Active = 1
AND StudentCoverageData.EffectiveDate <= #curdate
AND (StudentCoverageData.ExitDate IS NULL OR StudentCoverageData.ExitDate > #curdate)
ORDER BY StudentCoverageData.AsOfDate DESC)

Answer 1

All Tables in your subquery is exists in inner join clause, so you could rewrite your query like this:
;WITH temps AS
(
DECLARE #curdate DATETIME = GETDATE()
SELECT
SIS.StudentID, StudentCoverage.StudentCoverageDataID,
Student.FirstName, Student.LastName,
Student.DateOfBirth, Student.Gender,
ASMT.AssessmentDate,
ROW_NUMBER() OVER (PARTITION BY StudentCoverageData.StudentCoverageDataID ORDER BY StudentCoverageData.AsOfDate) AS RowIndex
FROM
SIS (NOLOCK)
INNER JOIN
SISMaster (NOLOCK) ON SISMaster.SISID = SIS.SISID
INNER JOIN
StudentCoverage (NOLOCK) ON StudentCoverage.StudentID = SIS.StudentID
INNER JOIN
Organization (NOLOCK) ON StudentCoverage.OrgID = Organization.OrganizationID
INNER JOIN
Student (NOLOCK) ON Student.StudentID = SIS.StudentID
INNER JOIN
StudentCoverageData (NOLOCK) ON StudentCoverageData.StudentCoverageID = StudentCoverage.StudentCoverageID
WHERE StudentCoverageData.Active = 1
AND StudentCoverageData.EffectiveDate <= #curdate
AND (StudentCoverageData.ExitDate IS NULL OR StudentCoverageData.ExitDate > #curdate)
)
SELECT * FROM temps t
WHERE t.RowIndex = 1