Trying to understand why these two queries which are logically the same do not use the same indexes.
QUERY #1
SELECT TOP 400
*
FROM AuditLog WITH ( NOLOCK )
WHERE CustomerID = 2379
AND PracticeID = 55
AND ( ( AuditTypeID = 4
AND EntityTypeID = 1022638
)
OR ( AuditTypeID = 6
AND SubEntityTypeID = 1022638
)
)
ORDER BY CreatedDate DESC
QUERY #2
SELECT TOP 400 *
FROM (
SELECT TOP 400
*
FROM AuditLog WITH ( NOLOCK )
WHERE CustomerID = 2379
AND PracticeID = 55
AND ( AuditTypeID = 4
AND EntityTypeID = 1022638
)
ORDER BY CreatedDate
UNION ALL
SELECT TOP 400
*
FROM AuditLog WITH ( NOLOCK )
WHERE CustomerID = 2379
AND PracticeID = 55
AND ( AuditTypeID = 6
AND SubEntityTypeID = 1022638
)
ORDER BY CreatedDate)sub
ORDER BY sub.CreatedDate