用触发器来实现Oracle的自增长列

1， 添加id列

-- ###############################################

-- add ID column for XXXXXXTABLE

-- ###############################################

declare

    v_cnt binary_integer := 0;

begin



    select count(1) into v_cnt

    from user_tab_columns e

    where e.table_name = 'XXXXXXTABLE'

      and e.column_name = 'ID';



    if( v_cnt = 0 ) then

        execute immediate 'alter table XXXXXXTABLE add ( ID int )';

    end if;

end;

/

2，给ID列赋值

-- ###############################################

-- set ID value with FXNDF_FIXING_POST_SEQ for XXXXXXTABLE

-- ###############################################

merge into XXXXXXTABLE u 

using ( 

select rowid rid, rownum rnum from XXXXXXTABLE 

) s 

on (u.rowid = s.rid) 

when matched then update set u.id = s.rnum ;

commit;

3， 添加序列

-- ###############################################

-- add FXNDF_FIXING_POST_SEQ

-- ###############################################

declare

    v_cnt binary_integer := 0;

    v_sql varchar2(500) := '';

    v_current_max int :=0;

    

begin

    

    select count(1) into v_cnt

    from user_sequences e

    where e.sequence_name  = 'XXXXXXTABLE_SEQ';

    

    if( v_cnt = 0 ) then

    

        select max(ID) into v_current_max from XXXXXXTABLE;

        

        select nvl(v_current_max,0) + 1 into v_current_max from dual;

        

        v_sql := 'CREATE SEQUENCE XXXXXXTABLE_SEQ MINVALUE ' || v_current_max || ' MAXVALUE 999999999999999999999999999 INCREMENT BY 1 START WITH ' || v_current_max;

        execute immediate v_sql;

                

    end if;

end;

/

4， 添加主键

-- ###############################################

-- add unit key on id for XXXXXXTABLE

-- ###############################################

declare

    v_cnt binary_integer :=0;

begin



    select count(1) into v_cnt

    from user_constraints e

    where e.table_name = 'XXXXXXTABLE'

      and e.constraint_name  = 'PK_XXXXXXTABLE';



    if( v_cnt = 0 ) then

        execute immediate 'alter table XXXXXXTABLE add constraint PK_XXXXXXTABLE primary key (ID)';

    end if;

end;

/

5， 添加before 触发器

-- ###############################################

-- add before insert trigger for XXXXXXTABLE

-- ###############################################

CREATE OR REPLACE TRIGGER TRG_XXXXXXTABLE_INST

  before insert ON XXXXXXTABLE   for each row

begin



select XXXXXXTABLE_SEQ.nextval into:new.ID from dual;



end TRG_XXXXXXTABLE_INST;

/