源地址：https://zhidao.baidu.com/question/66722841.html
1.不含大字段(clob等)的表格:
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--例子表格:create table test(a number,b number);--方法一:通过group by + rowid,效率低 delete from test t where t.rowid not in (select min(rowid) from test group by a, b);--方法二:通过 create + rename + distinct ,效率高create table test_tmp as select distinct * from test t;drop table test;alter table test_tmp rename to test; |
2.含大字段(clob等)的表格:
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--例子表格:create table test(a number,b clob);--clob 长度小于4000:select distinct t.a,to_char(t.b) as b from test t;--clob 长度大于4000:select * from test a where a.rowid = (select max(b.rowid) from test b where b.a = a.a and nvl(dbms_lob.compare(b.b, a.b), 0) = 0); |