how can we generate a ddl trigger for an alter statement

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Oracle

trigger

hi all,
for the sake of fun i want to create a trigger on schema. so i created a dynamic trigger which fired when a DDl operation performed on the trigger, everything goes fine except for alter statement. the issue is i want to capture that alter statement and disply the type of statement.
can anyone help me to solve this issue.
prefer not to use "like" operator

step 2:
now we will make some more complex situation like as our friend danielsql suggested something like before /after alter alter, before/after alter drop,.....
we have many operation which can done by using alter statement so if we create a constraint using alter statement, the trigger must display constraint type and constraint name.

thanks in advance

regards
Smart003