I'm probably not seeing the obvious so I keep making the same mistake. The table holds water chemistry data from multiple streams, sites within each stream, sampling dates, and many chemical constituents.
What I need to do are three things: 1.) Find the date and site for the maximum value of a specified constituent on a named stream. 2.) Find the values of that same constituent at other sites on the named stream on that same date. 3.) Find the date of the maximum value of a constituent for all sites on the named stream. Thinking the last the easiest to do, I submitted this query: select max(quant), site, sampdate from chemistry where stream = 'SheepCrk' and param = 'TDS' group by site, sampdate; but this gives me the value of each site and date, not the maximum for all dates at a specific site. Postgres tells me that both site and sampdate must be in the 'group by' clause. Obviously the syntax is more complex than I thought it would be and I would like a pointer to the correct way to write these queries. Rich -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
