用PL/SQL或者toad导入,插入数据后用一条sql语句去重 去重方式一(低效): select a.* from A_TEST a, (select min(id) as id from A_TEST t group by name) b where a.id = b.id; 去重方式一(高效): select * from (select a.*, rownum row_num from A_TEST a) x where x.row_num in (select min(rownum) from A_TEST t group by name) 可见,使用rownum的效率比使用id的效率要高,当表数据量很大的时候,差距会很明显。
去重方式一(低效):
select a.*
from A_TEST a, (select min(id) as id from A_TEST t group by name) b
where a.id = b.id;
去重方式一(高效):
select *
from (select a.*, rownum row_num from A_TEST a) x
where x.row_num in (select min(rownum) from A_TEST t group by name)
可见,使用rownum的效率比使用id的效率要高,当表数据量很大的时候,差距会很明显。