Intruder has a point, but it doesn't change the fact that the wing-to-fuselage joint need not be too heavy. It's the spar and joint(s) holding the wings to each other that's the heavy-duty structure.
I have seen:
One-piece wing, tip to tip, such as the A-4 and I believe A-6
Two-piece, joined at the centerline, example P-51 Mustang
Three-piece, with a center-section, example DC-3/C-47 Dakota