I am trying to understand the fields of various table and default list of metatags for the tables, currently being used in wordpress. Though google is showing up various results , but I need a detail one with list.
The WordPress codex has a pretty good diagram for you http://codex.wordpress.org/Database_Description
This seems to be a bit of a subjective question – as you dont say what you are trying to do or why you need such diagrams. It would be better to ask a new question please.
There is a bit of a collection of diagrams, schemas and other related stuff here
Looking for WordPress System Diagrams
And … at the end of the day — maybe you can write about your findings here to add to the knowledge.