DISTINCT and ORDER BY issue
От | terry@greatgulfhomes.com |
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Тема | DISTINCT and ORDER BY issue |
Дата | |
Msg-id | 001401c20268$fdff0c40$2766f30a@development.greatgulfhomes.com обсуждение исходный текст |
Ответы |
Re: DISTINCT and ORDER BY issue
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Список | pgsql-docs |
I know what I am doing wrong: The order by needs to match the DISTINCT fields. Here's what I am doing: Get the 10 most recent applications user has used to put in their "recently used" menu. So I need to ORDER BY user_app_access_log.access_stamp DESC But I want each record distinct, eg if the last 5 hits were all for the same app, I want 1 record returned for that. So if I put the access_stamp field in the DISTINCT field set, then I go back to getting repeats of apps, hence not 10 unique app names... I wonder if there is a way to use an aggregate function to just return the first value, (ignoring the rest of the group), and use the group by clause on the app_name? Any ideas is appreciated. Here is my query/error message: Error while executing the query; ERROR: For SELECT DISTINCT, ORDER BY expressions must appear in target list SELECT DISTINCT applications.app_name, applications.app_long_name, applications.app_url, user_access.in_new_window FROM applications, user_access, user_app_use_log WHERE user_app_use_log.user_id = '1' AND user_app_use_log.app_name != 'index' AND user_access.app_name = user_app_use_log.app_name AND user_access.user_id = user_app_use_log.user_id AND user_access.division_id = 'GGH' AND applications.app_name = user_access.app_name ORDER BY user_app_use_log.access_stamp DESC LIMIT 10" Thanks in advance Terry Fielder Network Engineer Great Gulf Homes / Ashton Woods Homes terry@greatgulfhomes.com
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