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Select TOP 1 on two fields
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De
04/02/2023 07:46:09
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
01686062
Message ID:
01686106
Vues:
57
Dmitry,

I follow such questions / discussions, because there are corners of SQL I am uncertain about or just ignorant. That said, In your shoes I'd never put the smart 1 query code in any of my apps

The basic OP question was clear and defined 2 selection steps. Why not KISS and code in 3 queries ? That way, you can be certain that you will not run afoul implementation differences or updates on esoteric SQL and if somebody else (or a future Dmitry...) touches that code it will still resolve to the result specced.
in Vfp there would be no need for even result cursor, better here as the JOIN is a filter
SELECT MAX(DATE_FLD) As mD FROM MyTable into Array aT_Date
SELECT MAX(ORDER_NO) AS mO FROM MyTable where DATE_FLD = aT_Date[1] into Array aT_Ord
SELECT fields_needed_list   FROM MyTable;
       where DATE_FLD = aT_Date[1] and ORDER_NO  = aT_Ord[1]
There is no need for checking _tally if there is at least 1 record, as filter is a self join.
So yes, ask questions- get smarter - but keep your code free of the answers ;-)

my 0.02€
thomas
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