What exactly are you trying to do?  Change all parts belonging to class ABC to class 123?

Before doing anything backup your BKICMSTR table  
    
Then you can run this script
It will change all parts that start with the word ORANGES (Item Number) to class 123
 
UPDATE BKICMSTR SET BKIC_PROD_CLASS = '123' WHERE BKIC_PROD_CODE LIKE 'ORANGES%'
 
or
 
UPDATE BKICMSTR SET BKIC_PROD_CLASS = '123' WHERE BKIC_PROD_CLASS = 'OLD'
 
it will change parts with OLD class to 123
 
 
 
 
Kelloggs

For the MTICMSTR  
 
UPDATE MTICMSTR SET MTIC_PROD_CLASS = '123' WHERE MTIC_PROD_CODE LIKE 'ORANGES%'
UPDATE MTICMSTR SET MTIC_PROD_CLASS = '123' WHERE MTIC_PROD_CLASS = 'OLD'
 
 
and dont forget to backcup!!!