SQL语句积累

alter user scott account unlock;

alter user scott identified by scott;

select table_name from user_tables;

select可以使用算术运算符 ：select sal*(1+0.1) from emp；

显示不重复的记录：select distinct job from emp;

设置条件，筛选数据行：select column_list from table_name where conditional_expression;

分组查询：select columns_list from table_name group by columns_list；(聚集函数：avg，count，sum)

排序查询：order by column_list desc/asc;(默认升序，降序使用desc关键字)

多表关联查询：内连接，外连接（左、右、全）