Chapter 9. SELECT Statement: SELECT Clause and Aggregation Functions
Introduction
The WHERE clause described in the previous chapter selects rows. The intermediate result from this clause forms a horizontal subset of a table. In contrast, the SELECT clause selects only columns and not rows; the result forms a vertical subset of a table.
The features, limitations, and use of the SELECT clause depend on the presence or absence of a GROUP BY clause. This chapter discusses table expressions without a GROUP BY clause. In Chapter 10, “SELECT Statement: The GROUP BY Clause,” which concentrates on the GROUP BY clause, we discuss the features of the SELECT clause when the table expression does contain a GROUP BY clause.
A large part of this chapter is devoted ...
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