数据库开发基础---常见面试题
create table a (t varchar2(20))
alter table a add s varchar2(20);
alter table a drop column s;
---删除子分区
alter table 分区表名
drop partition 子分区名;
delete from t a1 where a1.rowid not in (select max(a2.rowid) from t a2 group by a2.xx);commit;
Select Count(Decode(deptno, 20, '1', Null)) cnt_20,
Sum(Decode(deptno, 20, sal, 0)) sum_sal_20,
Count(Decode(deptno, 30, '1', Null)) cnt_30,
Sum(Decode(deptno, 30, sal, 0)) sum_sal_30
From emp
Where ename Like 'SMITH%'
and deptno in (20, 30);
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