Data: FactSet, Oracle filings ; Chart: Matt Phillips/AxiosThe colossal sums of money being spent on building out AI data centers can still put investors on edge. Oracle's results are the latest example of that. Why it matters: Investors are increasingly antsy about seeing at least some indication that the hundreds of billions of dollars now being spent on data centers will eventually turn into profitable investments. Oracle's results late Wednesday didn't offer them much.In the hyperscaler's fourth fiscal quarter, which ended May 31, the company spent a higher-than-expected $16.5 billion on capital expenditures, eating deeply into the company's — admittedly — fast-growing revenues.The fine print: Free cash flow — the cash the company generates from its core business, after backing out the costs of equipment, real estate and other investments — was a negative $1.87 billion during the quarter, bringing the sum of the cash it has burned over the last year to roughly $23.7 billion. Yes, but: The company's numbers weren't a disaster. It beat Wall Street analyst expectations for sales and earnings per share. The bottom line: Still, when your business burns through that much money, you often have to raise more.Oracle raised $43 billion in debt and equity raises during the fiscal year that finished in May. And it said it would likely raise another $40-odd billion over the next year, inclusive of a previously announced plan to sell about $20 billion more in equity.Investors didn't seem to like the sound of that. The stock tumbled about 11% in after-hours trading.