Obtener los códigos de los proveedores que venden al menos todas las partes vendidas por el proveedor S2.

Select distintc S#
From SPJ SPJX
Where not exists (Select *
From SPJ SPJY
Where S# = ‘S2’
And not exists (Select *
From SPJ
Where S# = SPJX.S#
And P# = SPJY.P#));

Algebra: SPJ [S#, P#, J#] divideby (SPJ where S# = ‘S2’) [P#]