Oracle入门基础（九）一一创建表和管理表

练习：查询每一年入职人数及总人数
SQL> select count(*) Total,
  2         sum(decode(to_char(hiredate,'yyyy'),'1980',1,0)) "1980",
  3         sum(decode(to_char(hiredate,'yyyy'),'1981',1,0)) "1981",
  4         sum(decode(to_char(hiredate,'yyyy'),'1982',1,0)) "1982",
  5         sum(decode(to_char(hiredate,'yyyy'),'1987',1,0)) "1987"
  6  from emp;

     TOTAL       1980       1981       1982       1987
---------- ---------- ---------- ---------- ----------
        14          1         10          1          2                                                                                                                                                  

SQL> --创建表
SQL> create table test1
  2  (tid number,tname varchar2(20));

SQL> --rowid 行地址
SQL> select rowid,empno,ename,sal from emp;

ROWID                   EMPNO ENAME             SAL
------------------ ---------- ---------- ----------
AAAMfPAAEAAAAAgAAA       7369 SMITH             800
AAAMfPAAEAAAAAgAAB       7499 ALLEN            1600                                                                                                                                                     

SQL> select * from emp where rowid='AAAMfPAAEAAAAAgAAJ';

     EMPNO ENAME      JOB              MGR HIREDATE              SAL       COMM     DEPTNO
---------- ---------- --------- ---------- -------------- ---------- ---------- ----------
      7844 TURNER     SALESMAN        7698 08-9月 -81           1500          0         30                                                                                                              

已选择 1 行。

SQL> --创建表：保存20号部门的员工
SQL> create table emp20 as select * from emp where deptno=20;

SQL> --创建表：员工号 姓名  月薪 年薪 部门名称
SQL> create table empinfo as select e.empno,e.ename,e.sal,e.sal*12 annsal,d.dname
           from emp e,dept d where e.deptno=d.deptno;

SQL> --修改表：增加新列，修改列，删除列，重命名列，重命名表
SQL> --增加新列
SQL> alter table test1 add photo blob;
SQL> --修改列
SQL> alter table test1 modify tname varchar2(40);
SQL> --删除列
SQL> alter table test1 drop column photo;
SQL> --重命名列
SQL> alter table test1 rename column tname to username;

SQL> --重命名表
SQL> rename test1 to test2;
SQL> --删除表
SQL> drop table TESTDELETE;

SQL> --查看回收站
SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
TESTDELETE       BIN$z6+GnIyhQtaIrbPpN1H99A==$0 TABLE        2016-10-06:15:24:14
SQL> --清空回收站
SQL> purge recyclebin;
回收站已清空。

SQL> select * from TESTSAVEPOINT;

       TID TNAME
---------- --------------------
         1 Tom
         2 Mary                                                                 

已选择 2 行。

SQL> drop table TESTSAVEPOINT;

表已删除。

SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
TESTSAVEPOINT    BIN$384BF4yOT+aAlXzC7eLPIA==$0 TABLE        2016-10-06:15:28:07
SQL> select * from TESTSAVEPOINT;
select * from TESTSAVEPOINT
              *
第 1 行出现错误:
ORA-00942: 表或视图不存在 

SQL> select * from tab;

TNAME                          TABTYPE  CLUSTERID
------------------------------ ------- ----------
DEPT                           TABLE
BIN$384BF4yOT+aAlXzC7eLPIA==$0 TABLE                                            

SQL> select * from "BIN$384BF4yOT+aAlXzC7eLPIA==$0";

       TID TNAME
---------- --------------------
         1 Tom
         2 Mary                                                                 

已选择 2 行。

SQL> --注意：管理员没有回收站
SQL> show user
USER 为 "SCOTT"
SQL> show recyclebin;
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
TESTSAVEPOINT    BIN$384BF4yOT+aAlXzC7eLPIA==$0 TABLE        2016-10-06:15:28:07
SQL> --闪回删除 ---> 回收站
SQL> flashback table TESTSAVEPOINT to before drop;

闪回完成。

SQL> show recyclebin;
SQL> select * from TESTSAVEPOINT;

       TID TNAME
---------- --------------------
         1 Tom
         2 Mary                                                                 

已选择 2 行。

SQL> create table test3
  2  (tid number,
  3   tname varchar2(20),
  4   gender varchar2(2) check (gender in ('男','女')),
  5   sal  number check (sal > 0)
  6  );

表已创建。

SQL> insert into test3 values(1,'Tom','男',2000);

已创建 1 行。

SQL> insert into test3 values(2,'Mike','啊',2000);
insert into test3 values(2,'Mike','啊',2000)
*
第 1 行出现错误:
ORA-02290: 违反检查约束条件 (SCOTT.SYS_C005393) 

SQL> create table student
  2  (
  3   sid number constraint student_pk primary key,
  4   sname varchar2(20) constraint student_name_notnull not null,
  5   gender varchar2(2) constraint student_gender check (gender in ('男','女')),
  6   email varchar2(40) constraint student_email_unique unique
  7                      constraint student_email_notnull not null,
  8   deptno number constraint student_fk references dept(deptno) on delete set null
  9  );
SQL> insert into student values(1,'Tom','男','tom@126.com',10);

已创建 1 行。

SQL> insert into student values(2,'Mike','男','tom@126.com',10);
insert into student values(2,'Mike','男','tom@126.com',10)
*
第 1 行出现错误:
ORA-00001: 违反唯一约束条件 (SCOTT.STUDENT_EMAIL_UNIQUE)