Anyway, if they bought Sun for MySQL (which I don't believe, it was probably for java), it's not because it was a direct competitor to Oracle DB but because MySQL occupied the low end market that they could never hope to occupy with Oracle DB.

That's exactly what they claimed at the time, but the MySQL documentation became unusable within a couple months of the purchase.

Some of Oracle's advanced features were superior to MySQL but that doesn't change the fact that both tools could get most database jobs done in an expert's hands.

I suspect we can at least agree MySQL used to be a threat to Oracle on the usability and adoption side of the market. MySQL was the go-to option, before their help pages stopped loading.