After you declare the cursor between the FOREACH and END
FOREACH statements, you enter a special, restricted form of the SELECT
statement known as a collection query.
A collection query is a SELECT statement that uses the
FROM TABLE keywords followed by the name of a collection variable.
The following figure shows this structure, which is known as a collection-derived
table. Figure 1. Collection-derived table.
FOREACH cursor1 FOR
SELECT * INTO pnt FROM TABLE(vertexes)
. . .
END FOREACH
The SELECT statement uses the collection variable vertexes as
a collection-derived table. You can think of a collection-derived
table as a table of one column, with each element of the collection
being a row of the table. For example, you can visualize the SET of
four points stored in vertexes as a table with four rows, such
as the one that the following figure shows. Figure 2. Table with four rows.
'(3.0,1.0)'
'(8.0,1.0)'
'(3.0,4.0)'
'(8.0,4.0)'
After the first iteration of the FOREACH statement in
the previous figure, the collection query selects the first element
in vertexes and stores it in pnt, so that pnt contains
the value '(3.0,1.0)'.
Tip: Because the collection variable vertexes contains
a SET, not a LIST, the elements in vertexes have no defined
order. In a real database, the value '(3.0,1.0)' might
not be the first element in the SET.