求一查询语句的写法？

[hnjhjzyyxgs]

有一个table：
ID 日期 内容
1 201208 ddd2
2 201202
3 201203
4 201204
5 201205 ddd2
6 201207 ddd2

数据中有以上内容
现在我想查询“日期字段”是连续的，并且连续3条“内容“字段 是空的数据；如下
2 201202
3 201203
4 201204

该查询语句该怎么写？

[programmerxiaocai]

select   日期 from  
  (select   count(*)   over   (PARTITION   by   DIFFDATE)   diffcount,id,日期
   from  
  (  
        SELECT   id,日期  ,add_months(日期   ,-ROW_NUMBER()   OVER(ORDER   BY   id,month)   )   DIFFDATE  
        FROM   tabname1  where  内容=null
  )   )where   diffcount   =   3

[大明湖畔_帅锅]

create table t1 (id number(10),month date,c varchar2(10));

insert into t1 values (1,date'2012-08-01','ddd2');
insert into t1 values (2,date'2012-02-01',null);
insert into t1 values (3,date'2012-03-01',null);
insert into t1 values (4,date'2012-04-01',null);
insert into t1 values (5,date'2012-05-01','ddd2');
insert into t1 values (6,date'2012-07-01','ddd2');
insert into t1 values (7,date'2012-06-01',null);
insert into t1 values (8,date'2012-09-01',null);
insert into t1 values (9,date'2012-10-01',null);
insert into t1 values (10,date'2012-12-01',null); 
insert into t1 values (11,date'2012-11-01','222'); 
insert into t1 values (12,date'2013-01-01',null); 
insert into t1 values (13,date'2013-02-01',null); 

select distinct id,to_char(month,'yyyy-mm') month  from  
(
         select count(*) over(partition by dif) diffcount,id,month
         from  
         (  
                  SELECT id,month ,
                         add_months(month,-row_number() over(order by month))  dif  
                  FROM  t1   
                  where c is null
          )   
)where diffcount   =   3 
order by month


    id    month
--------------------------
1	2	2012-02
2	3	2012-03
3	4	2012-04
4	10	2012-12
5	12	2013-01
6	13	2013-02

[xpingping]

with tb1 as (select ID ,日期 ,内容 from tb where 内容 is null order by ID) ,
select ID ,日期 ,内容 
from tb1
where add_months(日期,rownum)in
(select add_months(日期,rownum)
from tb1 
group by add_months(日期,rownum)
where count(1) =3)

[lxyzxq2008]

select ID,日期
from (
select ID, add_months(日期, level)
from table
where 内容 is null
connec by level <=3
)

[ssqtjffcu]

借用一下2楼数据

create table t1 (id number(10),month date,c varchar2(10));

insert into t1 values (1,date'2012-08-01','ddd2');
insert into t1 values (2,date'2012-02-01',null);
insert into t1 values (3,date'2012-03-01',null);
insert into t1 values (4,date'2012-04-01',null);
insert into t1 values (5,date'2012-05-01','ddd2');
insert into t1 values (6,date'2012-07-01','ddd2');
insert into t1 values (7,date'2012-06-01',null);
insert into t1 values (8,date'2012-09-01',null);
insert into t1 values (9,date'2012-10-01',null);
insert into t1 values (10,date'2012-12-01',null); 
insert into t1 values (11,date'2012-11-01','222'); 
insert into t1 values (12,date'2013-01-01',null); 
insert into t1 values (13,date'2013-02-01',null); 
 select id, month, c
   from (select id,
                month,
                c,
                count(1) over(partition by add_months(month, -rownum)) cn
           from t1
          where c is null)
  where cn = 3
         ID MONTH       C
----------- ----------- ----------
          2 2012-2-1    
          3 2012-3-1    
          4 2012-4-1    
         10 2012-12-1   
         12 2013-1-1    
         13 2013-2-1