oracle数据库查询2

            select
            ‘
            姓名为
            ‘|| ename||‘工作为‘||‘job‘||‘工资为‘|| sal as info from emp

            select lower（ename）as name from emp

            select decode(deptno,‘10‘,‘开发部‘,‘20‘,‘产品部‘,‘30‘,‘维护部‘)from emp

            select extract(year from sysdate) from dual

            select extract(year from sysdate) - extract(year from hiredate)  as age from emp

            select to_char(0.123,‘$0.9999‘)from dual

SELECT TO_CHAR(sysdate,‘YYYY"年"fmMM"月"fmDD"日" HH24:MI:SS‘)FROM dual;

            select ename,sal+nvl(comm,0) from emp
select ename,sal+nvl2(comm,comm,0) from emp

            select nullif(200,200) from dual

            select emp.*, row_number() over(order by sal desc ) as num from emp 

            select emp.*, rank() over(order by sal desc ) as num from emp 

            CREATE  USER  test  IDENTIFIED  BY  test;
GRANT  CONNECT , CREATE  SYNONYM TO test;
GRANT  SELECT   ON   SCOTT.EMP  TO test;
GRANT  DELETE  ON   SCOTT.EMP TO test;
GRANT  UPDATE  ON  SCOTT.EMP TO test;
        

            CREATE  SYNONYM   e   FOR  SCOTT.emp;

            select * from e

            CREATE   PUBLIC   SYNONYM  pub_emp FOR  SCOTT.emp;

            select * from  pub_emp 

            CREATE  sequence mysql
start with 
            1
            
increment by 
            1
            

create  table student(
        sid 
            int
             primary key,
        sname varchar(
            20
            )
) 

insert into student values(mysql.nextval,
            ‘
            张三
            ‘
            )

            select mysql.currval from dual
select * from student

grant create view to scott

            create  view dept_emp 

            as
            select dept.deptno,dname,loc,empno,ename,job,mgr,hiredate from emp join dept on emp.deptno=dept.deptno