php - Database Table Normalization -

table 1  id  student 1   ali 2   akram 3   aamir 4   adeel 5   aun  table 2  id  course 1   english 2   urdu 3   maths 4   physics 5   chemistry   table 3  id  stu_id   course_id 1   1          1 2   1          2 3   2          1 4   2          5 5   5          1 

q1: these tables normalized ?

q2: me remove duplicates table 3, suppose if table 2 have 1000 courses, , student id 1 , 2 enrolled in courses, table 3 large because of 2000 entries , there way reduce these ?

1. it normalized many-to-many relation;
2. yes max cardinality of many-to-many relation max students x max courses, nothing terrible;
3. in many-to-many relationships use multiple columns key of ids couple, not need id;
4. if duplicates mean fact have many equal fields in columns, not duplicates @ all. mean student has many courses , viceversa. has unique couple stu_id-course_id.

regards