Why is the database size larger than sum of table sizes
why database size is a way greater than the sum of table size in a database?

Databases contain lots of other things besides &quot;just&quot; your data.
Indexes are the largest and most obvious.  Every Index contains its key values, possibly some other stuff as well, depending on the Index type, and a pointer to the corresponding  Data record.
Every Table, and every Row within every Table, has some overhead associated with it, over and above the actual Data that you or I care about.
Then there's all the stuff that the DBMS creates for itself, like statistics tables, entire schemas for metadata, &quot;code&quot; objects like procedures and functions, and many, many more.