CREATE TABLE test(

ob_id VARCHAR(32),

ob_name VARCHAR(32)

);

INSERT INTO test VALUES('A001','A001-a');

INSERT INTO test VALUES('A001','A001-b');

INSERT INTO test VALUES('A001','A001-c');

INSERT INTO test VALUES('A001','A001-d');

INSERT INTO test VALUES('A002','A002-a');

INSERT INTO test VALUES('A002','A002-b');

INSERT INTO test VALUES('A002','A002-c');

INSERT INTO test VALUES('A002','A002-d');

COMMIT;

查询结果：

OB_ID      OB_NAME

A001        A001-a

A001        A001-b

A001        A001-c

A001        A001-d

A002        A002-a

A002        A002-b

A002        A002-c

A002        A002-d

如何实现下面的查询结果：

OB_ID      OB_NAME

A001          A001-a

　               A001-b

　              A001-c

　              A001-d

A002         A002-a

　              A002-b

　              A002-c

　             A002-d

方法一：

select decode(rownum,1,ob_id,5,ob_id) ob_id,ob_name from test;

方法二：

select decode(row_number() over(partition by ob_id order by ob_name),1,ob_id) ob_id,ob_name from test t;

方法三：

select decode(lag(ob_id) over(partition by ob_id order by ob_name), ob_id, null, ob_name) ob_id,ob_name from test;

方法四：

SELECT CASE WHEN m.rn=m.rn1 THEN NULL ELSE m.ob_id END ob_id, m.ob_name

FROM

(SELECT d.ob_id,d.ob_name,rn,LAG(d.rn) OVER(ORDER BY d.ob_id) rn1 FROM

(SELECT t.ob_id,t.ob_name,dense_RANK() OVER( ORDER BY t.ob_id) rn FROM  TEST t) d) m;

方法五：

select decode(t1.ob_name, v.name, t1.ob_id, ''), t1.ob_name

  from (select * from test t where rowid in (select min(rowid) from test  group by ob_id,ob_name)) t1

  join (select t.ob_id id, min(t.ob_name) name from test t group by t.ob_id) v on v.id = t1.ob_id

order by t1.ob_id, t1.ob_name;

方法六：

在sqlplus中

break on ob_id skip

select * from test;