I am not sure I correctly understand what you want. This is the value of d associated with a randomly chosen record from the group of records having the highest value of a tha also fulfills b == 1;
SELECT MAX(a),d FROM x WHERE b=1; If you want the value of d within each group of records sharing a value of c, try SELECT MAX(a),c,d FROM x WHERE b=1 GROUP BY c ORDER BY 1 DESC, 2 ASC; See also http://sqlite.org/lang_select.html "Side note: Bare columns in an aggregate queries. The usual case is that all column names in an aggregate query are either arguments to aggregate functions or else appear in the GROUP BY clause. A result column which contains a column name that is not within an aggregate function and that does not appear in the GROUP BY clause (if one exists) is called a "bare" column. Example: SELECT a, b, sum(c) FROM tab1 GROUP BY a; In the query above, the "a" column is part of the GROUP BY clause and so each row of the output contains one of the distinct values for "a". The "c" column is contained within the sum() aggregate function and so that output column is the sum of all "c" values in rows that have the same value for "a". But what is the result of the bare column "b"? The answer is that the "b" result will be the value for "b" in one of the input rows that form the aggregate. The problem is that you usually do not know which input row is used to compute "b", and so in many cases the value for "b" is undefined. Special processing occurs occurs when the aggregate function is either min() or max(). Example: SELECT a, b, max(c) FROM tab1 GROUP BY a; When the min() or max() aggregate functions are used in an aggregate query, all bare columns in the result set take values from the input row which also contains the minimum or maximum. So in the query above, the value of the "b" column in the output will be the value of the "b" column in the input row that has the largest "c" value. There is still an ambiguity if two or more of the input rows have the same minimum or maximum value or if the query contains more than one min() and/or max() aggregate function. Only the built-in min() and max() functions work this way." -----Ursprüngliche Nachricht----- Von: sqlite-users [mailto:sqlite-users-boun...@mailinglists.sqlite.org] Im Auftrag von Hamish Allan Gesendet: Montag, 03. April 2017 10:51 An: SQLite mailing list <sqlite-users@mailinglists.sqlite.org> Betreff: Re: [sqlite] Indexing WHERE with GROUP BY and ORDER BY Ah. My purpose is to determine "d for the most recent c with b=1", with "most recent" being "largest a". My query had been working for this, but I'd only been adding monotonically increasing values for "a" in my tests. I just tried doing otherwise and found that I had been relying on an implementation detail. Is there any way I can perform this collation at query time, or do I need to do it programmatically later on? Thanks, Hamish ___________________________________________ Gunter Hick Software Engineer Scientific Games International GmbH FN 157284 a, HG Wien Klitschgasse 2-4, A-1130 Vienna, Austria Tel: +43 1 80100 0 E-Mail: h...@scigames.at This communication (including any attachments) is intended for the use of the intended recipient(s) only and may contain information that is confidential, privileged or legally protected. Any unauthorized use or dissemination of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by return e-mail message and delete all copies of the original communication. Thank you for your cooperation. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
