How to limit group by to get n results per group?
SELECT yourtable.* FROM yourtable INNER JOIN ( SELECT id, GROUP_CONCAT (year ORDER BY rate DESC) grouped_year FROM yourtable GROUP BY id) group_max ON yourtable.id = group_max.id AND FIND_IN_SET (year, grouped_year) BETWEEN 1 AND 5 ORDER BY yourtable.id, yourtable.year DESC; Please see fiddle here.
When to use limit within group by in Excel?
Please note that if more than one row can have the same rate, you should consider using GROUP_CONCAT (DISTINCT rate ORDER BY rate) on the rate column instead of the year column. The maximum length of the string returned by GROUP_CONCAT is limited, so this works well if you need to select a few records for every group.
How to limit the number of rows in a query?
There are two ways to approach this: Have the client application run that query and fetch just the first N rows. Use that query as an inline view, and use ROWNUM to limit the results, as in SELECT * FROM ( your_query_here ) WHERE ROWNUM <= N. The second approach is by far superior to the first, for two reasons.
Is there a limit to the length of the string returned by group concat?
The maximum length of the string returned by GROUP_CONCAT is limited, so this works well if you need to select a few records for every group. The original query used user variables and ORDER BY on derived tables; the behavior of both quirks is not guaranteed.
How to select the first row of each group?
This solution also uses keep, but val and kind can also be simply calculated for each group without a subquery: KEEP…FIRST and KEEP…LAST are an Oracle-specific feature of aggregates — you can read about then here in the Oracle docs, or on ORACLE_BASE: Use a common table expression (CTE) and a windowing/ranking/partitioning function like ROW_NUMBER.
How to use limit within group by in SQL?
And then you could use FIND_IN_SET, that returns the position of the first argument inside the second one, eg. Using a combination of GROUP_CONCAT and FIND_IN_SET, and filtering by the position returned by find_in_set, you could then use this query that returns only the first 5 years for every id:
How to apply limit within group by problem?
If you want to filter for a particular CID, just add AND “CID” = ‘C1’ or whatever to the inner WHERE clause. BTW, your test data is insufficient, since it can never have more than two rows for any CID with score > 20 anyway. This is not actually a GROUP BY problem (you’re not aggregating values).
When to sort, when to group and when to summarize?
The following tips will help you discern when to sort, when to group, and when and how to summarize. For detailed information on each clause and operator, see Books Online. More often than not, all your data really needs is a little order.