fix: use default (#4)

Author: zchpeter

schema/class.sql

@@ -2,7 +2,7 @@ CREATE TABLE "public"."class" (
     "class_no" integer DEFAULT nextval('public.class_no_seq'::regclass) NOT NULL,
     "class_name" text NOT NULL,
     "grade" integer NOT NULL,
-    "student_limit" integer NOT NULL,
+    "min_credit" integer NOT NULL DEFAULT 0,
     CONSTRAINT "class_pkey" PRIMARY KEY (class_no),
     CONSTRAINT "class_grade_check" CHECK (grade > 0 AND grade <= 12)
 );

schema/student.sql

@@ -4,7 +4,7 @@ CREATE TABLE "public"."student" (
     "first_name" text NOT NULL,
     "last_name" text NOT NULL,
     "gender" text NOT NULL,
-    "email" text NOT NULL,
+    "email" text NOT NULL DEFAULT '',
     CONSTRAINT "student_pkey" PRIMARY KEY (student_no),
     CONSTRAINT "student_gender_check" CHECK (gender = ANY (ARRAY['M'::text, 'F'::text]))
 );