Introduction






Introduction

The processing of a table expression begins at the FROM clause. In fact, this is the starting point of processing a table expression, which is why this clause is discussed in detail first.

In this chapter, we describe the basic features of the FROM clause. In previous chapters, you saw many examples of this clause. The FROM clause is an important clause because each table from which we "use" columns in the other clauses should be specified here. By "using," we mean, for example, that a column appears in a condition or in the SELECT clause. Simply, in the FROM clause, we specify the tables from which the result of a table expression will be retrieved.

The FROM clause has many different forms. We start this chapter with the simplest form.



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