[英]Get the top row after order by in Oracle Subquery
I have a table student(id, name, department, age, score). 我有一个表学生(身份证,姓名,部门,年龄,分数)。 I want to find the youngest student who has the highest(among the youngest students) score of each department.
我想找到每个系最高(最年轻的学生)得分最年轻的学生。 In SQL Server, I can use following SQL.
在SQL Server中,我可以使用以下SQL。
select * from student s1
where s1.id in
(select s2.id from student s2
where s2.department = s1.department order by age asc, score desc top 1).
However, in Oracle, you cannot use the order by clause in subquery and there is no limit/top like keyword. 但是,在Oracle中,您不能在子查询中使用order by子句,并且没有limit / top like关键字。 I have to join the student table with itself two times to query the result.
我必须自己加入学生表两次才能查询结果。 In oracle, I use following SQL.
在oracle中,我使用以下SQL。
select s1.* from student s1,
(select s2.department, s2.age, max(s2.score) as max_score from student s2,
(select s3.department, min(s3.age) as min_age from student s3 group by s3.department) tmp1 where
s2.department = tmp1.department and s2.age = tmp1.min_age group by s2.department, s2.age) tmp2
where s1.department =tmp2.department and s1.age = tmp2.age and s1.score=tmp2.max_score
Does anyone have any idea to simplify the above SQL for oracle. 有没有人有任何想法为oracle简化上述SQL。
try this one 试试这个
select * from
(SELECT id, name, department, age, score,
ROW_NUMBER() OVER (partition by department order by age desc, score asc) srlno
FROM student)
where srlno = 1;
In addition to Allan's answer, this works fine too: 除了艾伦的回答,这也很好:
select *
from (SELECT *
FROM student
order by age asc,
score desc)
where rownum = 1;
In addition to Bharat's answer, it is possible to do this using ORDER BY in the sub-query in Oracle (as point out by Jeffrey Kemp): 除了Bharat的回答之外,还可以在Oracle的子查询中使用ORDER BY来做到这一点(正如Jeffrey Kemp指出的那样):
SELECT *
FROM student s1
WHERE s1.id IN (SELECT id
FROM (SELECT id, ROWNUM AS rn
FROM student s2
WHERE s1.department = s2.department
ORDER BY age ASC, score DESC)
WHERE rn = 1);
If you use this method, you may be tempted to remove the sub-query and just use rownum = 1
. 如果您使用此方法,您可能想要删除子查询,只需使用
rownum = 1
。 This would result in the incorrect result as the sort would be applied after the criteria (you'd get 1 row that was sorted, not one row from the sorted set). 这将导致不正确的结果,因为排序将在标准之后应用(您将获得已排序的1行,而不是排序集中的一行)。
select to_char(job_trigger_time,'mm-dd-yyyy') ,job_status from
(select * from kdyer.job_instances ji INNER JOIN kdyer.job_param_values pm
on((ji.job_id = pm.job_id) and (ji.job_spec_id = '10003') and (pm.param_value='21692') )
order by ji.job_trigger_time desc)
where rownum<'2'
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.