Re: minus and intersect functionality

A generalised minus query using NOT EXISTS:

SELECT symbol
 FROM symbol_table
 WHERE NOT EXISTS
(SELECT *

   FROM trade
   WHERE tsymbol = symbol_table.symbol)

Alternatively, "Minus JOIN", assuming the Symbol column is unique in both tables:

SELECT S.symbol
 FROM symbol_table AS S
 LEFT JOIN trade AS T
  ON S.symbol = T.tsymbol
  AND T.tsymbol IS NULL

Generalised intersection, using EXISTS:

SELECT symbol
 FROM symbol_table
 WHERE EXISTS
(SELECT *

   FROM trade
   WHERE tsymbol = symbol_table.symbol)

Or just an INNER JOIN if Symbol is unique in both tables:

SELECT S.symbol
 FROM symbol_table AS S
 JOIN trade AS T
  ON S.symbol = T.tsymbol

-- 
David Portas
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