Continuing the discussion from Created / Modified Timestamps:
Currently CREATED_TIME() exists, but not CHANGED_TIME().
I suppose CHANGED_TIME shouldn not be updated when table schema is altered, e.g. when ‘{username} caused a change due to modifying a column’ message is logged in records’ histories.
+1 for this
adding some love to hit 20 characters 
See thread here: Date Field AutoUpdate on Last Change/Addition
Unfortunately you’re right that we don’t have an equivalent formula for CHANGED_TIME()
For anyone that stumbles on this thread, the LAST_MODIFIED_TIME() formula makes this possible!
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