I am also interested in techniques to streamline managing a group of, say, 300 reports.
We use Custom SQL in most of our Tableau data connections and when we have a database schema change -- even something as simple as renaming a column -- I have to manually edit each data connection in every workbook (assuming none use a shared data connection).
Here are some two options for you:-
1. First, refresh the data connection (F5). Right-click the dimension or measure in the connection, select "Replace References...", then select the name of the new column
2. Maybe you can create a view in the database with the same name of the column as the old version, edit the connection in Tableau and make the source table be the new view instead of the old table.
But if i have 300 reports and it's using different queries as i said that, then again i need to create 300 views right?
I think you will only need 1 view if you only changed a column in a single table. You'll only need to create a new view for each table changed in your database schema. All you have to do is to create a new view with the same name as the old table (which might need you to change the old table name to something else) and the connections will automatically get the data from this new view with the column changed renamed to match the old column name used before. If you can't change the old table name, then create a new view and change the source table name in each data connection to match the name of the new view. (N.B. It is always recommended that you make the presentation layer you use in your BI reports data-connections as a set of views and not tables because this allows you to change the database schema without affecting the presentation layer design ... views are flexible because you can keep the same column names while changing the underlying query for source columns ... this is the best practice).
If you are using custom-SQL data connections then you'll only need to create new views for the tables in the FROM clause which were altered.
However, if you just have a few data-connections shared between the reports (that's why data-connection reuse is recommended in most cases) then you can use the first technique in my first message to alter the connection ... which will be very simple.
Hope this makes sense.