Hi,
The difference is that the operation of tMySQLSDCELT is available inside a MySql database, however, tMySQLSCD can be used in two MySQL DB.
For example, I have two DB. One is "test" and the other is "test2". If I want to use the SCD technology between "test"and "test2". I only use tMySQLSCD as the solution. Hope it will helpful for you.
Best regards
Sabrina