Update cdc.sql

[sarwarbhuiyan]

We do need the before returned so as to be able to do "undo" in the changelog query processing

PR checklist:

• Did you run ClangFormat ?
• Did you separate headers to a different section in existing community code base ?
• Did you surround proton: starts/ends for new code in existing community code base ?

Please write user-readable short description of the changes:

[sarwarbhuiyan]

@jovezhong this is the better one since it includes the undo capability

[jovezhong]

probably a typo for type converting. Also please change the format to make the script more compact.