I m planning to add a key column index in one of the existing non clustered index in a big table which have millions of rows rather than create a new non clustered index. Is that any way for me to know how much the extra space consumed by the index by adding a new key column in existing non clustered index and is that there is any data/index ratio best practices, as I know its better not to have more than 5 index per table.
Just to be clear, I need to explain to storage team extra space that consumed by index after add the new column , then only I can add the column to existing index