# 注释-select(筛选)select * from student;# 根据需求查询返回列信息select studentName,gender from student;# 使用别名来处理列名称 asselectstudentName as 学生姓名,gender 性别fromstudent;#筛选语句where: 依靠关系运算符进行筛选select * from student where classNo 202202;select * from student where classNo 202202;select * from student where classNo 202202;select * from student where classNo ! 202202;select * from student where classNo 202202;select * from student where classNo (202202100);# and与or示例select * from student where birthday 2005-01-01 and gender 男;#组合式写法select * from select * from student where birthday 2005-01-01) a where a.gender 男;# orselect * from student where phone 13800138019 or phone 13800138009;#order by 排序 adc 正序默认 desc 倒序select * from student order by birthday;select * from student order by birthday desc;#年龄最大的也就是出生最早的先筛选在排序select * from student where gender 男 order by birthday;# 最年轻的女孩select * from student where gender 女 order by birthday desc;# 去重关键字 diatink []select distinct national 民族 from student;