How many oboes are in a band?

In top-tier orchestras you usually 4 oboists, though typically one of them is officially the English Horn player.

A typical band or orchestra has two to three oboes.

It's usually the number of oboes required by a composer in any given piece. A Haydn symphony may require two oboes (or in some of his symphonies: NONE) while a tone-poem by Richard Strauss may require triple WW or more.