SQL Server query to show read and write ratios on user database tables. A useful tool to reference and utilize before database performance tuning.

--use <DATABASE_NAME>;
--go

select object_name(s.object_id) as table_name,
    SUM(user_seeks + user_scans + user_lookups) as reads,
    SUM(user_updates) as writes,
    SUM(user_seeks + user_scans + user_lookups + user_updates) as total_io,
    case
        when SUM(user_seeks + user_scans + user_lookups + user_updates) > 0
            then round(SUM(user_seeks + user_scans + user_lookups) * 100 / SUM(user_seeks + user_scans + user_lookups + user_updates), 0)
        else 0
    end as read_ratio,
    case
        when SUM(user_seeks + user_scans + user_lookups + user_updates) > 0
            then SUM(user_updates) * 100 / SUM(user_seeks + user_scans + user_lookups + user_updates)
        else 0
    end as write_ratio
from sys.dm_db_index_usage_stats as s
inner join sys.indexes as i
    on s.object_id = i.object_id
       and i.index_id = s.index_id
where objectproperty(s.object_id, 'IsUserTable') = 1
group by s.object_id
order by total_io desc, writes desc, write_ratio desc;