Because 5 pretty smart users of both sites thought it would be more relevant and valuable on the database administrators site. Just because a database-related question is on-topic on Stack Overflow does not make it off-topic everywhere else, nor does it necessarily make Stack Overflow the best place for it. Stack Overflow database-related questions tend to be simple things like "how do I get the just-inserted identity value?" and endless streams of "how do I split a comma-separated value?" The topic of the question, and even more so the details in Mikael's answer, make it a question that is more complex than average. Don't you want it on the site where it can get the best answers, rather than remain on the site where you asked? I'm not sure I understand why it matters which site it's on as long as you received a satisfactory answer.

http://dba.stackexchange.com/help/on-topic

Because 5 pretty smart users of both sites thought it would be more relevant and valuable on the database administrators site. Just because a database-related question is on-topic on Stack Overflow does not make it off-topic everywhere else, nor does it necessarily make Stack Overflow the best place for it. Stack Overflow database-related questions tend to be simple things like "how do I get the just-inserted identity value?" and endless streams of "how do I split a comma-separated value?" The topic of the question, and even more so the details in Mikael's answer, make it a question that is more complex than average. Don't you want it on the site where it can get the best answers, rather than remain on the site where you asked? I'm not sure I understand why it matters which site it's on as long as you received a satisfactory answer.

https://dba.stackexchange.com/help/on-topic