load csv file content into mysql table with validation

This is actually pretty common SQL: you either want to insert or update, yes? So you need two statements (one for update, one for insert) and a way to tell if it should be inserted. What you really need is a unique key that will never be duplicated for the individual record (can be a composite key) and two statements, like this:

UPDATE right SET
   right1 = left1,
   right2 = left2,
   etc
FROM the_import_table right
LEFT JOIN the_existing_data left ON left.key = right.key
WHERE right.key IS NOT NULL --note that I write in TSQL

INSERT INTO right (
   right1,
   right2,
   etc
) SELECT
   left1,
   left2,
   etc
FROM left
LEFT JOIN right on left.key = right.key
WHERE right.key IS NULL

Note that you can use composite keys using a set of ANDed values in the WHERE, and note that you're not updating the composite keys but you are probably inserting the composite keys. This should be good to get you a start. Before you ask for clarification update your question with actual code.

MySQL has specific insert syntax to deal with duplicate rows.