Intersection table representing the resolution of a many to many relationship.

position_in_wb_s (FSK, M: CHAR VARYING(19))
position_in_wb_t (M: CHAR VARYING(16))
other_material_s (FSK, M: CHAR VARYING(19))

other_material.position_in_wellbore
Specifies the present or original location of this material.
position_in_wellbore.other_material
Specifies various materials which are found at this position in the wellbore.
position_in_wb_s: Implements a foreign key to a row in one of the tables projected from entity position_in_wellbore depending on the value of the next column (See below).
position_in_wb_t: Defines the name of the referenced table. Possible values are defined in @position_in_wellbore.
other_material_s: Defines a foreign key to table other_material.