CREATE TABLE "passengers" (
    "id" INTEGER,
    "first_name" TEXT NOT NULL,
    "last_name" TEXT NOT NULL,
    "age" INTEGER NOT NULL,
    PRIMARY KEY("id")
);

CREATE TABLE "checkins" (
    "id" INTEGER,
    "checkin_data" NUMERIC NOT NULL DEFAULT CURRENT_TIMESTAMP,
    "flight" TEXT NOT NULL,
    PRIMARY KEY("id")
);

CREATE TABLE "airlines" (
    "id" INTEGER,
    "name" TEXT NOT NULL,
    "concourse" TEXT,
    PRIMARY KEY("id")
);

CREATE TABLE "flights" (
    "id" INTEGER,
    "flight_number" INTEGER NOT NULL,
    "airline" TEXT NOT NULL,
    "departure_code" TEXT NOT NULL,
    "arrival_code" TEXT NOT NULL,
    "departure_date" NUMERIC NOT NULL,
    "arrival_date" NUMERIC NOT NULL,
    PRIMARY KEY("id"),
    FOREIGN KEY("airline") REFERENCES "airlines"("name")
)