Oracle与DB2中序列处理

1、序列定义    
   ORACLE:   

             CREATE SEQUENCE <sequence_name>

          INCREMENT BY <integer>

              START WITH <integer>

           MAXVALUE <integer> / NOMAXVALUE

           MINVALUE <integer> / NOMINVALUE

              CYCLE / NOCYCLE

              CACHE <#> / NOCACHE

              ORDER / NOORDER;   
    
   DB2:    

             CREATE SEQUENCE <sequence-name> 

                 AS data-type                           默认 As Integer
              START WITH <numeric-constant>   
          INCREMENT BY <numeric-constant>               默认 INCREMENT BY 1
           MINVALUE <numeric-constant> | NO MINVALUE    默认 NO MINVALUE
           MAXVALUE <numeric-constant> | NO MAXVALUE    默认 NO MAXVALUE
           NO CYCLE | CYCLE                             默认 NO CYCLE
           CACHE <numeric-constant> | NO CACHE          默认 CACHE 20
           NO ORDER | ORDER                             默认 NO ORDER

2、序列取值
   取下一个值：
      ORACLE: 序列.NEXTVAL
      DB2:    NEXTVAL FOR 序列 或 NEXT VALUE FOR 序列
   取当前值：
      ORACLE: 序列.CURRVAL
      DB2:    PREVIOUS VALUE FOR 序列  或 PREVVAL FOR 序列

3、序列设置开始值
     ORACLE：取得下一个值；先设置步长（下一个值 与 设置的开始值之间差）；取得下一个值；再把步长修改成原来值
     DB2：ALTER SEQUENCE 序列名  RESTART WITH 下一值

3、修改
     ORACLE：
 修改最大值    ALTER SEQUENCE <sequence_name> MAX VALUE <integer>
 修改最小值：  ALTER SEQUENCE <sequence_name> MIN VALUE <integer> （此值需要比当前值小）
 修改步长：    ALTER SEQUENCE <sequence_name> INCREMENT BY <integer>;
 修改CACHE值： ALTER SEQUENCE <sequence_name> CACHE <integer> | NOCACHE
 修改循环属性: ALTER SEQUENCE <sequence_name> <CYCLE | NOCYCLE>
 修改排序属性：ALTER SEQUENCE <sequence_name> <ORDER | NOORDER>

     DB2： 
 修改最大值    ALTER SEQUENCE <sequence_name> MAX VALUE <numeric-constant> | NO MAXVALUE
 修改最小值：  ALTER SEQUENCE <sequence_name> MIN VALUE <numeric-constant> | NO MINVALUE （此值需要比当前值小）
 修改步长：    ALTER SEQUENCE <sequence_name> INCREMENT BY <numeric-constant>;
 修改CACHE值： ALTER SEQUENCE <sequence_name> CACHE <numeric-constant> | NO CACHE
 修改循环属性: ALTER SEQUENCE <sequence_name> <CYCLE | NO CYCLE>
 修改排序属性：ALTER SEQUENCE <sequence_name> <ORDER | NO ORDER>
 从新计数：    ALTER SEQUENCE <sequence_name> RESTART | RESTART WITH <numeric-constant>

3、DROP 
    ORACLE： DROP SEQUENCE <sequence_name>; 
    DB2：    DROP SEQUENCE <sequence_name>;