CREATE TABLE "student" (
   "student_id" SERIAL NOT NULL PRIMARY KEY,
   "nazwa" varchar(255)
);

CREATE TABLE "kurs" (
   "kurs_id" SERIAL NOT NULL PRIMARY KEY,
   "kurs_kod" varchar(10),
   "nazwa" varchar(255)
);

CREATE TABLE "student_kurs" (
   "student_id" integer,
   "kurs_id" integer,
   CONSTRAINT "fk_student_kurs_student_id"
      FOREIGN KEY ("student_id")
      REFERENCES "student"("student_id"),
   CONSTRAINT "fk_student_kurs_kurs_id"
      FOREIGN KEY ("kurs_id")
      REFERENCES "kurs"("kurs_id")
);

CREATE UNIQUE INDEX "idx_student_kurs_unikalny"
   ON "student_kurs"("student_id", "kurs_id");