How to summarize one-to-many spatial join results with the same ID while each ID does have multiple string features

After using the One-to-many option in the spaital join tool, I received a shapefile which includes 13 million rows and several columns. I am wondering how I can calculate the sum of different values of "BldfClass" (see the picture) that have the same "osmid" which is their ID. For instance, how many "Land Only" value of the "BldgClass" column does exist in the "osmid" 81765871. In general, I do have 35000 different ID numbers (osmid), and also the "Bldgclass" column includes about 40 different values. The reason that I have 13 million rows is that the ID number has been repeated for various rows and I want to summarize all of the information regarding each ID number. It would be something similar to the Pivot table of Excel.