Uses for Subqueries
At this point, you should have a pretty good understanding of the concept of using a subquery either to generate an output column or to perform a complex comparison in a WHERE clause. The best way to give you an idea of the wide range of uses for subqueries is to list some problems you can solve with subqueries and then present a robust set of examples in the Sample Statements section.
Build Subqueries as Column Expressions
As mentioned earlier in this chapter, using a subquery to fetch a single value from a related table is probably more effectively done with a JOIN. When you consider aggregate functions, however, subqueries to fetch the result of a function calculation make the idea much more interesting. We’ll explore ...
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