Try

SELECT cost, site FROM crs1 c1 ;
	WHERE cost = (SELECT MIN(cost) FROM crs1 WHERE site = c1.site)

>Suppose you have issued a sql-select which returns several records containing the fields COST and SITE among others. Then suppose you want to select from this result the minimum COST and its corresponding SITE. As in:
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>select min(cost), site from crs1
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>This produces an error Group clause invalid. How should this second select be structured?
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