Plotting the intersection of multiple surfaces with WolframAlpha

Question

I want to plot the intersection of two surfaces like in this post.

But if I enter the much simplified expression

ContourPlot3D[{x^2 + y^2 + z^2 - 4=0, xy=1}, {x, -2, 2}, {y, -2, 2}, {z, -2, 2}]

he gives me an error message, you can try it here, so what am I doing wrong?

Answer 1

Just because it works in Mathematica, doesn't mean it'll work in Wolfram|Alpha. From the FAQ:

Can I use Mathematica code in Wolfram|Alpha?

Yes. Most small pieces of Mathematica code will work in Wolfram|Alpha. In most cases, you can mix the Mathematica code with pseudocode and math.

If you have access to Mathematica, you need to use == instead of =, and you also need to use x*y else Mathematica will treat xy as its own variable.