根据特定字段中的最大值将MAX（）结果限制为一行

Question

Of course my data set is more complex, but this is essentially what I have:

+--------+--------+-------+
| SEQ_NO | FILTER | VALUE |
+--------+--------+-------+
|      1 | 'A'    |     5 |
|      2 | 'A'    |    10 |
|      3 | 'A'    |    15 |
+--------+--------+-------+

Here is my query:

  SELECT MAX(SEQ_NO)
       , FILTER
       , VALUE
    FROM TABLE
GROUP BY FILTER
       , VALUE

This returns my entire data set. How can I alter my query so that it only returns the record with the highest SEQ_NO ?

Answer 1

SELECT t1.*
FROM Table AS t1
INNER JOIN
(
    SELECT MAX(SEQ_NO) MAXSeq
           , FILTER
           , VALUE
        FROM TABLE
    GROUP BY FILTER
           , VALUE
) t2  ON t1.SEQ_NO = t2.MAXSeq 
        AND t1.FILTER = t2.FILTER 
        AND t1.VALUE = t2.VALUE

Or using row_number :

SELECT *
FROM
(
   SELECT *, 
     row_number() over(partition by FILTER, VALUE 
                       order by SEQ_NO desc) as rn
   FROM table
) t 
WHERE rn = 1

Answer 2

From Oracle 12C:

SELECT SEQ_NO
       , FILTER
       , VALUE
    FROM TABLE
 ORDER BY SEQ_NO DESC
FETCH FIRST 1 ROWS ONLY;

Answer 3

If I understand correctly, you want the top SEQ_NO per filter?

i've created this in SQL Server and converted to Oracle

SELECT  a.SEQ_NO,
        a.FILTER,
        a.VALUE
FROM    (
            SELECT  SEQ_NO,
                    FILTER,
                    VALUE,
                    MAX(SEQ_NO) OVER (PARTITION BY FILTER) m
            FROM    TABLE
        ) a
WHERE   SEQ_NO = m

Answer 4

Using mysql

SELECT SEQ_NO
       , VALUE
       , FILTER
    FROM TABLE
Order by SEQ_NO DESC LIMIT 1

Answer 5

You can use ROWNUM in oracle:

select *
from  
  ( select * 
    from yourTable
    order by SEQ_NO desc )  as t
where ROWNUM = 1;

Answer 6

This should work

SELECT TOP 1 *
FROM TABLE
ORDER BY SEQ_NO DESC