-- 创建临时表空间
create temporary tablespace test_temp
tempfile 'E:\app\tablespace\test_temp.dbf'
size 32m
autoextend on
next 32m maxsize 2048m
extent management local;

--创建数据表空间
create tablespace test
logging
datafile 'E:\app\tablespace\test.dbf'
size 32m
autoextend on
next 32m maxsize 2048m
extent management local;

-- 创建用户
create user chentao identified by chentao default tablespace test temporary tablespace test_temp;

--给用户援权
grant resource,connect,dba to test;

--给表添加字段,可批量
alter table tab_name add(col_name1 varchar2(20),col_name2 varchar2(20));

-- 删除字段,可批量
alter table tab_name drop column col_name1,col_name2;

-- 添加字段描述
comment on column tab_name.username 	IS '用户名';

-- 更改字段默认值
alter table tab_name modify username default 'chentao'

-- 删除约束
alter table tab_name drop constraint foreign_key_name

-- 查询用户下所有表
select 'Drop table '||table_name||';' from all_tables where owner='数据库用户名';

select * from all_tables where table_name='sales_card_body'

-- 查询某个时段的数据
select * from (
  select * from tbl_name as of timestamp to_timestamp('2011-7-22 13:00:00','yyyy-mm-dd hh24:mi:ss')
) where head_id is not null;


-- 更改某表字段类型,考虑到字段本身有数据所以采用此方法更新
ALTER TABLE LOG_ACTIVITY_MAIN ADD(CARD_ID_TEMP NUMBER);
alter table tab_name add(col_name_temp number);
-- Add/modify columns
update tab_name set col_name_temp=col_name,colname=null;
commit;
alter table tab_name modify col_name varchar2(15);
update tab_name set col_name=col_name_temp,col_name_temp=null;
commit;
alter table tab_name drop column col_name_temp;
alter table tab_name modify col_name not null;

-- 创建序列
create sequence seq_tab_name_id
minvalue 1
maxvalue 999999999999999999999999999
start with 1
increment by 1
cache 20;


Oracle毫秒日期转换
--毫秒转日期
select 1197902428593/1000/60/60/24+to_date('1970-01-01 08:00:00', 'yyyy-MM-dd hh:mi:ss') from dual; --1197900835625

--日期转毫秒
select (to_date('2006-1-1 12:30:25', 'yyyy-mm-dd hh:mi:ss') - TO_DATE('1970-1-1', 'yyyy-mm-dd')) * 24 * 60 * 60 * 1000 resulttime from dual;

-- 日期相减,减一年
select sysdate - 365 from dual;

-- for 的应用
set serveroutput on;
begin
dbms_output.put_line('打印倒三角形');
for i in 1..9 loop
      for j in reverse i..9 loop     --reverse对值进行从大到小的循环
        dbms_output.put('*');
      end loop for_j;
        dbms_output.new_line;--用于在缓冲区中添加换行符
      end loop for_i;
end;

-- 判断一个表是否存在
declare
    nums number;
begin
    select count(1) into nums from user_tables where table_name= 'TMP_CAT';
    if nums>0 then
      execute immediate 'drop table TMP_CAT';
    end if;
end;

?-- 修改tablename1表中的 column1字段值为tablename2表的column1,如果column1为空,则默认值为1
update tablename1 tn set tn.column1 =
       nvl((select max(tn2.column1) from tablename2 tn2 where tn.id = tn2.id),1)