sqlite constraint base another table - sqlite

Question

I have 2 tables CarParking and ParkingArea. On ParkingArea I need to save the MaxPricePerDay, and on CarParking I have to save the cost. I try to write constraint that the cost is under or equal to MaxPricePerDay base on the AID columnn.
How can I do that?
CREATE TABLE "CarParking" (
"StartTime" TIMESTAMP NOT NULL,
"EndTime" TIMESTAMP NOT NULL,
"Cost" INTEGER NOT NULL,
"CID" INTEGER NOT NULL,
"AID" INTEGER NOT NULL,
FOREIGN KEY("CID") REFERENCES "Car"("CID")
ON DELETE CASCADE,
FOREIGN KEY("AID") REFERENCES "ParkingArea"("AID")
ON DELETE SET NULL,
CONSTRAINT time_car CHECK(StartTime<=EndTime),
PRIMARY KEY("StartTime","CID")
);
CREATE TABLE "ParkingArea" (
"MaxPricePerDay" INTEGER NOT NULL,
"PricePerHour" INTEGER NOT NULL,
"Name" TEXT NOT NULL,
"AID" INTEGER UNIQUE NOT NULL,
"Neighborhood" INTEGER NOT NULL,
PRIMARY KEY("AID"),
FOREIGN KEY ("Neighborhood") REFERENCES "Neighborhood" ("NID")
ON DELETE CASCADE
);

Answer 1

Since CHECK constraints can't have subqueries, one way is using a trigger instead.
CREATE TRIGGER check_max_price BEFORE INSERT ON CarParking
BEGIN
SELECT raise(ABORT, 'Exceeded MaxPricePerDay')
FROM ParkingArea
WHERE aid = new.aid AND new.Cost > MaxPricePerDay;
END;
is a starting point; you'll have to tweak the calculation to see if the cost is too much as appropriate.
If your cost can be updated after a row is inserted, you'll want a similar trigger for UPDATE.