correlated-subquery - Read For Learn

SQL Server “cannot perform an aggregate function on an expression containing an aggregate or a subquery”, but Sybase can

One option is to put the subquery in a LEFT JOIN: Perhaps a better option would be to use SUM with CASE: SQL Fiddle Demo with both

SQL ZOO List each continent and the name of the country that comes first alphabetically

when you use x.name=y.name you are comparing country name from x with the country name from y if both instances have the same country name. That basically would just return you the full table x. You want to use x.continent=y.continent because you only want to compare the country name of an instance from x with the country name of … Read more

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