CREATE TABLE Meal (

-- Meal has MealId,
MealId                                  int IDENTITY NOT NULL,
PRIMARY KEY(MealId)

) GO

CREATE TABLE Service (

-- maybe Service earned a tip of Amount and Amount has AUDValue,
AmountAUDValue                          decimal NULL,
-- Service involves Meal and Meal has MealId,
MealId                                  int NOT NULL,
-- Service involves Waiter and Waiter has WaiterNr,
WaiterNr                                int NOT NULL,
PRIMARY KEY(WaiterNr, MealId),
FOREIGN KEY (MealId) REFERENCES Meal (MealId)

) GO

CREATE TABLE WaiterTip (

-- WaiterTip involves Amount and Amount has AUDValue,
AmountAUDValue                          decimal NOT NULL,
-- WaiterTip involves Meal and Meal has MealId,
MealId                                  int NOT NULL,
-- WaiterTip involves Waiter and Waiter has WaiterNr,
WaiterNr                                int NOT NULL,
PRIMARY KEY(WaiterNr, MealId),
FOREIGN KEY (MealId) REFERENCES Meal (MealId)

) GO