Sun announced Tuesday that its $1 billion deal to buy open-source database vendor MySQL has closed, and with the news came a bold proclamation from Sun CEO Jonathan Schwartz.

"In my view, this is the most important acquisition in Sun's history, and the most important in the modern software industry," Schwartz said during a conference call.

MySQL's CEO, Marten Mickos, is now senior vice president of a new database group within Sun's software division. "In terms of the business model, technology, and culture, the fit with Sun is perfect," he said.

During the call, Schwartz acknowledged that Sun's acquisition plans aren't over, but said future deals will likely concern "more tuck-in assets."

"MySQL was the crown jewel of the open-source marketplace. As far as we can see, there are no more higher-value assets we can acquire," he said.

Despite Schwartz's characterization of the MySQL deal as a pinnacle moment for Sun, its price tag is much lower than other acquisitions, such as the $4.1 billion it paid for StorageTek in 2005.

In addition, Schwartz's boasts belie the fact that deals from other vendors -- such as the $8.5 billion Oracle is plunking down for middleware vendor BEA Systems, an acquisition announced in January -- dwarf the MySQL buy.

Schwartz acknowledged that "in terms of relative valuation, the financials are one way to look at it."

But "looking forward, MySQL is profound for a very basic reason," he said. "It has a customer base in the millions, if not tens of millions."

However, since the acquisition was first announced, users have urged Sun to deal with various performance and scalability limitations within MySQL.

Teams are already working on such issues, particularly regarding scalability, said Rich Green, executive vice president of Sun's software group, in an interview following the conference call. "It's a really high priority for us to deal with the improved scalability issue. We're all over it." Green declined to provide a release road map.

Despite the potential scale of the business Sun could build around MySQL, its partner relationships with makers of proprietary databases will not be affected, Green asserted.

"The simple answer is that's going to go unchanged," he said. "We've built an enormous customer base with companies like Oracle and Sybase. We're going to go full speed in those partnerships."

In an interview, Mickos said his initial job will be to ensure business runs as usual for existing MySQL customers: "The first thing is to do no harm."

The new Sun executive cited the "energy" generated by MySQL's user base as one of its key strengths.

One question is how being acquired will alter MySQL's relationship with its community. "I think it will change. I think it will improve," Mickos said, adding, "there will always be someone upset with something. If nobody is upset, that means nobody cares."

Sun is now offering subscriptions and services for MySQL's full range of products. It is also introducing MySQL Enterprise Unlimited. For a flat annual fee, customers can deploy an unlimited number of MySQL Enterprise Servers.

More than 100 million copies of MySQL's database have been downloaded and distributed, according to Sun. The daily rate has grown from 50,000 to more than 60,000 since it announced its plans to buy MySQL, Sun said.

This story was updated on February 26, 2008