Change Drupal 7 decimal field scale or precision

We wanted to change the MRP field 'field_per_item_cost' from DECIMAL (12,2) to DECIMAL (12,3).

 The following SQL Query will do the trick:  

ALTER TABLE field_data_field_per_item_cost MODIFY field_per_item_cost_value DECIMAL(12,3); 

ALTER TABLE field_revision_field_per_item_cost MODIFY field_per_item_cost_value DECIMAL(12,3); 

UPDATE field_config SET data = REPLACE(data, '"scale";s:1:"2";', '"scale";s:1:"3";') WHERE field_name = 'field_per_item_cost'; 

UPDATE field_config_instance SET data = REPLACE(data, '"scale";s:1:"2";', '"scale";s:1:"3";') WHERE field_name = 'field_per_item_cost'; 

To show config data from HEX to utf8, we can use the following SQL code 

SELECT CONVERT(data USING utf8) FROM field_config WHERE field_name = 'field_per_item_cost'