经典SQL（2）

1、经典的查询语句
2、经典的字定义函数
3、经典的与业务相关的存储过程
等等
1、 跟踪当前对话下用户的SQL脚本
select sql_text from v$sqltext_with_newlines where (hash_value,address)
in (select sql_hash_value,sql_address from v$session where sid=&sid)
order by address,piece;
SID
由这得到
select sid,machine from v$session;
======
desc table;检查表结构
select * from tab where tabtype='TABLE';显示当前用户下的所有表。
select count(*) from table;显示此表的数据行数；
spool c:\tony.txt;日记路径
spool off;关闭记录后可以看到日记文件里的内容。
alter table stu add(classid number(2));添加字段
alter table stu modify(xm varchar2(12));修改字段的长度
alter table stu drop column sal;
drop table stu;
rename student to stu;
alter table student drop column sal; alter table stu add(salary number(7,2));
insert into stu values('A001','张三','男','01-5月-05',10);
insert into stu(xh,xm,sex) values ('A003','JOHN','女');
insert into student(xh,xm,sex,birthday) values ('A004','MARTIN','男',null);
修改
update
update stu set sex='女' where xh='A001';
update student set sex='男'，birthday='1980-04-01'where xh='A001';
update student set classid=20 where birthday is null;
delete from stu;drop table student;delete from stu where xh='A001';
truncate table stu;删除表中的所有记录，表结构还在不写日记无法找回记录
select * from stu;
select * from student where classid like '1%';
select * from student where xh like '%A%';
select * from student where xh like 'A%';
select * from student where xh like '%A';
select * from student where xh = 'A%';
select * from student order by birthday;
select * from student order by birthday desc,xh asc; --按birthday 降序 按xh升序(asc/默认)
select * from student where sex='女' or birthday='1999-02-01';
select * from student where sex='女' and birthday='1999-02-01';
select * from student where salary > 20 and xh <> 'B002'; (!=)
oracle
函数的学习
单行函数  返回值只有一个
分组