oracle数据库的增删改查
增:
①增加部分字段:insert into table (字段1,字段2)values(v1,v2)
②增加全部字段:insert into table values(v1,v2)
删:
delete * from table where id='123'
改:
①修改部分字段:update table set 字段='value' where id='123'
查:
①条件查询:select * from table where id='123'
②分页查询:
select a.* from (select id , rownum rn from table )a where a.rn<10 and a.rn>5
函数:
select count (studentId) from student group by classId;//查出每个班级的学生的数量;根据班级编号分组
select stu.className from student stu ,(select classId,count (studentId) count from student group by classId)b where stu.classId=b.classId order by b.count desc;//根据班级学生量倒叙查出班级名称
select nickname,user_name,
case when user_rank = '5' then '经销商'
when user_rank = '6' then '代理商'
when user_rank = '7' then 'vip'
else '注册用户' end as user_rank
from at_users