SQL 数据查询 | 数据库技术基础官方章节 9.4.4 SQL 数据查询，共 26 个知识点。本章知识点 SELECT FROM WHERE DISTINCT ORDER BY GROUP BY HAVING 聚合函数 COUNT SUM AVG MAX MIN INNER JOIN LEFT JOIN RIGHT JOIN 子查询 相关子查询 IN EXISTS ANY ALL UNION LIKE NULL 判断 分组查询