SQL在线基本练习
https://www.liaoxuefeng.com/wiki/1177760294764384
https://www.nowcoder.com/ta/sql-quick-study
SQL在线进阶练习
https://www.nowcoder.com/ta/sql-advanced
SQL在线练习-大厂面试
https://www.nowcoder.com/ta/sql-factory-interview