DC8 (and I think DC9 also) had wings built as left and right units each including half the centre section, which were then joined in the middle to make a complete wing and the fuselage was lifted over the wing and lowered on to it and then permanently joined. This is not the norm however. The 707 wing was also a one piece separate structure attached to the fuselage by 4 bottle pins (large hollow pins). Most aircraft and probably all modern designs, have the wing centre section made integral with the fuselage with the wings being made as separate units which are then spliced to the centre section. A cruciform shaped fitting is often embodied in the centre section top and bottom joints and the wing skins slide into it. Typically there are only a couple of rows of fasteners, albeit high strength one's, that attach the wing to the centre section at the exterior splice.