网上查看分段查询的例子，用的最多的是LAG和LEAD统计函数，Lag和Lead函数可以在一次查询中取出同一字段的前N行的数据和后N行的值。这种操作可以使用对相同表的表连接来实现，不过使用LAG和LEAD有更高的效率。例如：create table TEST( GRADE NUMBER not null, STUID VARCHAR2(4));insert into test (GRADE, STUID)values (1, '1001');insert into test (GRADE, STUID)values (2, '1002');insert into test (GRADE, STUID)values (3, '1003');insert into test (GRADE, STUID)values (4, '1005');insert into test (GRADE, STUID)values (5, '1006');insert into test (GRADE, STUID)values (6, '1008');insert into test (GRADE, STUID)values (7, '1010');insert into test (GRADE, STUID)values (8, '1011');insert into test (GRADE, STUID)values (9, '1012');insert into test (GRADE, STUID)values (10, '1015');insert into test (GRADE, STUID)values (11, '1017');insert into test (GRADE, STUID)values (12, '1018');insert into test (GRADE, STUID)values (13, '1020');insert into test (GRADE, STUID)values (14, '1021');insert into test (GRADE, STUID)values (21, '1022');commit;select (case when k – kk > 0 then kk || '~' || k else k || '' end) jg from (select k k, k2 k2,lag(k2, 1, (select min(stuid) from test)) over(order by k) as kk –1001起始值，，对k列排序，取K2列中下一位是那个数字from (select *from (select id1, id2, id2 – id1,(case when id2 – id1 = 1 then 1 else id1 end) k, –如果不连续显示开始ID(case when id2 – id1 = 1 then id1 else id2 end) k2 –如果不连续显示结束IDfrom (select to_number(stuid) id1,lead(to_number(stuid), 1, (select min(stuid) from test)) over(order by stuid) as id2 –1001起始值，获取id1下个idfrom test))where k > 1 –只取不连续数字)) g
就是对虚怀若谷谦虚谨慎八个字真正理解的人，
