1SELECT name, COUNT(email)
2FROM users
3GROUP BY email
4HAVING COUNT(email) > 1
1CREATE TABLE new_table LIKE original_table;
2INSERT INTO new_table SELECT * FROM original_table;
1ALTER TABLE Table1
2ADD SubCategory2 {Type of subcategory 1} {NULL|NOT NULL}
3UPDATE Table1 SET SubCategory2 = SubCategory;
4