Update form A according to values in form B

I have form A with about 300,000 rows; Form B has about 500 rows.

Form B column1 has 500 distinct values , used as foreign key in one of the columns in Form A. Now, I want to update Form A column2 if column1's value is found in Column B. How should I go about this?

This is very easy with any RDBMS but with Zoho scripting, how should I do it?

Thanks.