>>It should unless you have not numeric data. What error do you get?
>
>After verification, while the command to CAST as INT would work, one of the records has a special character in it, probably an error in the code at some time, which allowed non numeric value to be entered in that field. So, I would need to look for a more enhanced command to convert only numeric values, and if a non-digit character is found in the field, to consider that as 0.

Use ISNUMERIC() function

UPDATE Client SET Amount2 = 
CASE WHEN ISNUMERIC(Amount ) = 1 THEN CAST(Amount AS INT) ELSE 0 END)