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Oracle ???????

? Oracle ????????????????? SQL ?????????????????????????????????????????????

1. ??????

?????????????????????? SQL ???

delete from twhere rowid not in (select min(rowid) from t group by null);

????????????? rowid ?????????????????????????????????????????

2. ????

????????????????????????????????????

-- ???????insert into t_back (select distinct mobile from t)-- ????drop table t-- ?????????rename t_back to t;

?????????????????????????????????????????????????????

3. ?????

???????????????????????? SQL ???

-- ???1???2????????select field1, field2, count(*) from tgroup by field1, field2having count(*) > 1where field3 = 'value';-- ????1???2?????delete from t awhere (select field1, field2 from t_b group by field1, field2 having count(*) > 1)

4. ?????

????????????????????????????

-- ???????????create table t_temp as(select field1, field2, max(rowid) as dataid from tgroup by field1, field2);-- ????1???2?????delete from t awhere (select field1, field2 from t_temp);

5. ??????

???????rowid????????????????

-- ???? `rowid`select max(b.rowid) from t bwhere a.field1 = b.field1 and a.field2 = b.field2;-- ?? `rowid` ?????????delete from t awhere a.rowid != (select max(b.rowid) from t bwhere a.field1 = b.field1 and a.field2 = b.field2);

6. ???????

???????????????????????

-- ????????????insert into t_back (select * from t);-- ????drop table t;-- ??????create table t as select * from t_back;

7. ????

?????????????????? SQL ???

-- ??????delete from twhere column_name is null;

8. ??????

???????????????????

-- ??????delete from t awhere a.rowid in (select rowid from t_b group by null order by rowid);

9. ?????

?????????????????

-- ?????? `rowid` ???create table t_optimized as(select a.rowid, a.* from t agroup by a.rowid);-- ????drop table t;-- ?????????rename t_optimized to t;

10. ????

????????????????????????

-- ?????????insert into t_new (select * from t);-- ????drop table t;-- ?????????rename t_new to t;

?????????????????? Oracle ??????????????????????????????????

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