SQL 我如何在 Oracle 中排名前 1？
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How do I do top 1 in Oracle?
提问by Gold
回答by mcpeterson
If you want just a first selected row, you can:
如果您只想要第一个选定的行，您可以：
select fname from MyTbl where rownum = 1
You can also use analytic functions to order and take the top x:
您还可以使用解析函数对顶部 x 进行排序和取值：
select max(fname) over (rank() order by some_factor) from MyTbl
回答by Damian Leszczyński - Vash
SELECT *
FROM (SELECT * FROM MyTbl ORDER BY Fname )
WHERE ROWNUM = 1;
回答by MSK
With Oracle 12c(June 2013), you are able to use it like the following.
使用Oracle 12c（2013 年 6 月），您可以像下面这样使用它。
SELECT * FROM MYTABLE
--ORDER BY COLUMNNAME -OPTIONAL
OFFSET 0 ROWS FETCH NEXT 1 ROWS ONLY
回答by Sarath Avanavu
You could use ROW_NUMBER()with a ORDER BYclause in sub-query and use this column in replacement of TOP N. This can be explained step-by-step.
您可以在子查询中使用ROW_NUMBER()withORDER BY子句并使用此列替换TOP N. 这可以逐步解释。
See the below table which have two columns NAMEand DT_CREATED.
请参阅下表，其中包含两列NAME和DT_CREATED。
If you need to take only the first two dates irrespective of NAME, you could use the below query. The logic has been written inside query
如果您只需要取前两个日期而不考虑NAME，您可以使用以下查询。逻辑已经写在查询里面
-- The number of records can be specified in WHERE clause
SELECT RNO,NAME,DT_CREATED
FROM
(
-- Generates numbers in a column in sequence in the order of date
SELECT ROW_NUMBER() OVER (ORDER BY DT_CREATED) AS RNO,
NAME,DT_CREATED
FROM DEMOTOP
)TAB
WHERE RNO<3;
RESULT
结果
In some situations, we need to select TOP Nresults respective to each NAME. In such case we can use PARTITION BYwith an ORDER BYclause in sub-query. Refer the below query.
在某些情况下，我们需要TOP N为每个选择结果NAME。在这种情况下，我们可以使用PARTITION BY与ORDER BY子查询子句。请参阅以下查询。
-- The number of records can be specified in WHERE clause
SELECT RNO,NAME,DT_CREATED
FROM
(
--Generates numbers in a column in sequence in the order of date for each NAME
SELECT ROW_NUMBER() OVER (PARTITION BY NAME ORDER BY DT_CREATED) AS RNO,
NAME,DT_CREATED
FROM DEMOTOP
)TAB
WHERE RNO<3;
RESULT
结果
回答by Suman
You can do something like
你可以做类似的事情
SELECT *
FROM (SELECT Fname FROM MyTbl ORDER BY Fname )
WHERE rownum = 1;
You could also use the analytic functions RANKand/or DENSE_RANK, but ROWNUMis probably the easiest.
您还可以使用分析函数RANK和/或DENSE_RANK，但ROWNUM可能是最简单的。
回答by a'r
select * from (
select FName from MyTbl
)
where rownum <= 1;
回答by OMG Ponies
Use:
用：
SELECT x.*
FROM (SELECT fname
FROM MyTbl) x
WHERE ROWNUM = 1
If using Oracle9i+, you could look at using analytic functions like ROW_NUMBER() but they won't perform as well as ROWNUM.
如果使用 Oracle9i+，您可以考虑使用诸如 ROW_NUMBER() 之类的分析函数，但它们的性能不如 ROWNUM。
回答by Vikas Hardia
To select the first row from a table and to select one row from a table are two different tasks and need a different query. There are many possible ways to do so. Four of them are:
从表中选择第一行和从表中选择一行是两个不同的任务，需要不同的查询。有很多可能的方法可以做到这一点。其中四个是：
First
第一的
select max(Fname) from MyTbl;
Second
第二
select min(Fname) from MyTbl;
Third
第三
select Fname from MyTbl where rownum = 1;
Fourth
第四
select max(Fname) from MyTbl where rowid=(select max(rowid) from MyTbl)
回答by user2607028
I had the same issue, and I can fix this with this solution:
我有同样的问题，我可以用这个解决方案解决这个问题：
select a.*, rownum
from (select Fname from MyTbl order by Fname DESC) a
where
rownum = 1
You can order your result before to have the first value on top.
您可以先对结果进行排序，以便将第一个值放在最前面。
Good luck
祝你好运
