tagDatabase not taged

Here is about my changelog:

<sqlFile  path=“view1.sql” relativeToChangelogFile=“true” />

drop view v_test


I set some tags in changelog and want to rollback to “v0” “v1” …  with “rollback tag-name”.when I executed the changelog, I found the table databasechangelog in database is like this 

Obviously,the tag ‘v2’ is missed. so I can’t rollback to ‘v2’. and why this happened?    

In above case, my database is mysql. when I changed to oracle,it works well.  I guess the problem maybe about the precision of the column dateexecuted .  It is different in mysql and oracle