In my Wordpress Blog site i have installed too much plugin and remove also many plugins. In database table "wp_options" size increases approx 13MB and there are many rows which are unused at this time. So I want to remove these unused rows from "wp_options" table and optimized this table as much as low size. But HOW?
There is a plugin called - Clean Options which promises to remove all unused entries from wp_options table. NOTE - that plugin hasn't been updated for 2 years, you must do backup before using it.
To remove all data manually
You have to manually look into database for unused tables or rows and use the SQL query to delete those permanently from the database.
That SQL query will select all rows with prefix
i guess you've already dug the path. from where you've seen that table is already taken 13MB? certainly from some GUI tools and possibly using phpMyAdmin. You can clean the unused rows from there.
you can also check the disabled plugins which fields they added. if those plugins did not uninstall/remove those rows, you can delete it yourself and this way you create less risks of breaking stuffs.