I have secondary indexes on a few tables which were unused.Tables are of large size (>100 million rows)In that case,how much the impact will be there on the database?
The below should give the space occupied by the secondary index on any table. First you need to collect demographics
INTO qcd ALL;
,SUM(RowCount*AvgRowSize) AS SizeInBytes
FROM qcd.DataDemographicsView ddv
GROUP BY 1,2,3,4