How to use condition in column in group by with agg request

it's a bit hard to explain, i dont know how to use a condition in a column-select attribute in a SQL who have group by and aggregat functions...

I want to return grouping with session :

• The earliest Startdate (Using MIN aggregat, is ok it work)
• The most recent EndDate (Using MAX aggregat, is ok it work)
• The TradeKP which corresponds on the line who have "." in TradeID. (It's the problem how to do that?) For information, one session can have 1 to 600 lines. One session only have one line with "." in TradeID The line who have "." maybe anywhere and therefore has no link with the date. The number total of row of this table can reach up to 500 millions of lines.

Exemple :

I tried with this request, but it doesn't work :

SELECT session,
       MIN(DateStart) as beginning,
       MAX(DateEnd) as ending,
       MAX(tradeKP) as TradingMaster
FROM SCHEMA.TRADES
GROUP BY session

You can take value of column tradeID only for rows with condtition tradeID='.' ignoring (null) all other's.

Try

SELECT session,
       MIN(DateStart) as beginning,
       MAX(DateEnd) as ending,
       MAX(case when tradeID='.' then tradeKP end) as TradingMaster
FROM SCHEMA.TRADES
GROUP BY session