Grazie a @marc_s per la risposta. Avevo bisogno di conoscere i dati rispetto allo spazio dell'indice, quindi sono andato avanti e ho ampliato la query per includerlo.
SELECT TableName
, SUM(DataRowCounts) AS DataRowCounts
, SUM(DataTotalSpaceGB) AS DataTotalSpaceGB
, SUM(DataSpaceUsedGB) AS DataSpaceUsedGB
, SUM(DataUnusedSpaceGB) AS DataUnusedSpaceGB
, SUM(IndexRowCounts) AS IndexRowCounts
, SUM(IndexTotalSpaceGB) AS IndexTotalSpaceGB
, SUM(IndexSpaceUsedGB) AS IndexSpaceUsedGB
, SUM(IndexUnusedSpaceGB) AS IndexUnusedSpaceGB
, SUM(DataTotalSpaceGB) + SUM(IndexTotalSpaceGB) AS TotalSpaceGB
FROM
(
SELECT t.NAME AS TableName
, i.type_desc AS IndexType
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS DataTotalSpaceGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS DataSpaceUsedGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS DataUnusedSpaceGB
, CASE WHEN i.type_desc IN ('CLUSTERED', 'CLUSTERED COLUMNSTORE', 'HEAP') THEN SUM(p.Rows) ELSE 0 END AS DataRowCounts
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.total_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS IndexTotalSpaceGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.used_pages) * 8) / 1024.00), 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS IndexSpaceUsedGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN CAST(ROUND(((SUM(a.total_pages) - SUM(a.used_pages)) * 8) / 1024.00, 2)/1000 AS NUMERIC(36, 2)) ELSE 0 END AS IndexUnusedSpaceGB
, CASE WHEN i.type_desc = 'NONCLUSTERED' THEN SUM(p.Rows) ELSE 0 END AS IndexRowCounts
FROM sys.tables t
INNER JOIN sys.indexes i ON t.OBJECT_ID = i.object_id
INNER JOIN sys.partitions p ON i.object_id = p.OBJECT_ID AND i.index_id = p.index_id
INNER JOIN sys.allocation_units a ON p.partition_id = a.container_id
LEFT JOIN sys.schemas s ON t.schema_id = s.schema_id
WHERE t.NAME NOT LIKE 'dt%'
AND t.is_ms_shipped = 0
AND i.OBJECT_ID > 255
AND s.Name = 'dbo' --update this filter
AND t.Name = 'MyTable'
GROUP BY t.Name
, i.type_desc
) x
GROUP BY TableName
ORDER BY TotalSpaceGB DESC