一、创建序列：

        create sequence <序列名称>
         start with <起始数>
         increment by <增长量>
         [maxvalue  值]
         [minvalue  值]
         [cycle 当到达最大值的时候，将继续从头开始]
         [Nocycle  -- 一直累加，不循环]　　
      [Cache ]

二、Oracal的lpad函数

     lpad( string1, padded_length, [ pad_string ] )
     其中string1是需要粘贴字符的字符串
     padded_length是返回的字符串的数量，如果这个数量比原字符串的长度要短，lpad函数将会把字符串截取成padded_length;

     pad_string是个可选参数，这个字符串是要粘贴到string1的左边，如果这个参数未写，lpad函数将会在string1的左边粘贴空格。
    例如：
          

lpad('tech', 7);

将返回' tech'

lpad('tech', 2);	将返回'te'
lpad('tech', 8, '0');	将返回'0000tech'
lpad('tech on the net', 15, 'z');	将返回 'tech on the net'
lpad('tech on the net', 16, 'z');	将返回 'ztech on the net'

三、Oracal的to_char函数

The following are date examples for the to_char function.

to_char(sysdate, 'yyyy/mm/dd');	would return '2003/07/09'
to_char(sysdate, 'Month DD, YYYY');	would return 'July 09, 2003'
to_char(sysdate, 'FMMonth DD, YYYY');	would return 'July 9, 2003'
to_char(sysdate, 'MON DDth, YYYY');	would return 'JUL 09TH, 2003'
to_char(sysdate, 'FMMON DDth, YYYY');	would return 'JUL 9TH, 2003'
to_char(sysdate, 'FMMon ddth, YYYY');	would return 'Jul 9th, 2003'

You will notice that in some examples, the format_mask parameter begins with "FM". This means that zeros and blanks are suppressed.
This can be seen in the examples below.

to_char(sysdate, 'FMMonth DD, YYYY');	would return 'July 9, 2003'
to_char(sysdate, 'FMMON DDth, YYYY');	would return 'JUL 9TH, 2003'
to_char(sysdate, 'FMMon ddth, YYYY');	would return 'Jul 9th, 2003'

The zeros have been suppressed so that the day component shows as "9" as opposed to "09".

四、例：

DROP SEQUENCE test_mySeq;
DROP TABLE test;

CREATE SEQUENCE test_mySeq
        START WITH 1001
        INCREMENT BY 1
        MAXVALUE 9999999999
        MINVALUE 1
        CYCLE
        NOCACHE;
CREATE TABLE test
(
  ID          VARCHAR2(10) not null,
  orderid     VARCHAR2(20) not NULL
);

INSERT INTO test(ID,orderid)VALUES(to_char(SYSDATE,'yyyymmdd'),'HG-'||to_char(SYSDATE,'yyyymmdd')||lpad(test_mySeq.nextval, 8, '0'));
COMMIT;

SELECT * FROM test ORDER BY orderid ASC;

转自：http://blog.csdn.net/jkant/archive/2009/04/24/4106687.aspx
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