For the variables field type some of the values are sql longblob.  Whne trying to update the missing value fields where the code of "NA" migrated but the code definition did not i needed to find and update those variables.

So first I modified phpadmin /etc/phpmyadmin/config.inc.php with ( see https://groups.drupal.org/node/134269)

Show 1000 rows instead of 30 by default
$cfg['MaxRows'] = 1000;
# Show BLOB data as a string not hex.
$cfg['DisplayBinaryAsHex'] = false;
# Show BLOB data in row detail pages.
$cfg['ProtectBinary'] = false;
# Show BLOB data on table browse pages.  Hack to hardcode all requests.
$_REQUEST['display_blob'] = true;

Now that I could see the values I needed to search and replace the values with only "NA". I eventually found that I could search with

Select *
FROM `field_data_field_variables`
WHERE `field_variables_missing_values` LIKE '%s:2:"NA"%'

And combining to update the values

UPDATE `piedeims7dev`.`field_data_field_variables` SET `field_variables_missing_values` = 'a:1:{s:2:"NA";s:7:"missing";}' WHERE `field_variables_missing_values` LIKE '%s:2:"NA"%'

And it worked.

Note that the blob is array of strings (s: number of characters:"value")