MySQL – How to Fix Issues Importing .sql File

juergen d's answer is of course correct; however, considering your error message, you can also add to your SQL file at the beginning line like:

USE your_database_name;

This should also do the job and let you import under the Workbench.

When you are using mysqldump, the exported file will be saved in the current folder. It doesn't matter under what path it is. Just when importing from command line you need to be at the same folder or specify path to the file. But this isn't the case when you are using visual tool like Workbench, where you need to select the file from folder tree anyway.

Use MySQL Workbench. You can right-click a table and select "Send to SQL Editor" --> "Create Statement". This way no table "properties" will be forgotten to add (including CHARSET or COLLATE).
With this huge amount of data I'd recommend cleaning up either the table or the data structure you use (a good DBA comes handy). If not possible:

• rename the table (ALTER) and create a new one with the CREATE script you get from Workbench. You can also extend that query with the new field you need
• BULK LOAD the data from the old table to the new one:

  SET FOREIGN_KEY_CHECKS = 0;
  SET UNIQUE_CHECKS = 0;
  SET AUTOCOMMIT = 0;
  INSERT INTO new_table (fieldA, fieldB, fieldC, ..., fieldN)
     SELECT fieldA, fieldB, fieldC, ..., fieldN
     FROM old_table
  SET UNIQUE_CHECKS = 1;
  SET FOREIGN_KEY_CHECKS = 1;
  COMMIT;
  

  
  This way you avoid indexing/etc to run record by record. The "update" to the table still will be slow (as the amount of data is huge) but this is the fastest way I can think of.
  
  EDIT: Read this article to get details about the commands used in the above sample query ;)