FOR LOOP Statement

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13.33 FOR LOOP Statement

With each iteration of the FOR LOOP statement, its statements run, its index is either incremented or decremented, and control returns to the top of the loop. The FOR LOOP statement ends when its index reaches a specified value, or when a statement inside the loop transfers control outside the loop or raises an exception.

Topics

Syntax

for_loop_statement ::=

Description of for_loop_statement.eps follows

Description of the illustration for_loop_statement.eps

(statement ::=)

Semantics

for_loop_statement

index

Name for the implicitly declared integer variable that is local to the FOR LOOP statement. Statements outside the loop cannot reference index. Statements inside the loop can reference index, but cannot change its value. After the FOR LOOP statement runs, index is undefined.

See Also:

"FOR LOOP Index"

[ REVERSE ] lower_bound .. upper_bound

lower_bound and upper_bound must evaluate to numbers (see "Lower Bound and Upper Bound"). PL/SQL evaluates lower_bound and upper_bound once, when the FOR LOOP statement is entered, and stores them as temporary PLS_INTEGER values, rounding them to the nearest integer if necessary.

If lower_bound equals upper_bound, the statements run only once.

If lower_bound does not equal upper_bound when the FOR LOOP statement begins to run, then:

If REVERSE is omitted:

If lower_bound is greater than upper_bound, the statements do not run, and control transfers to the statement after the FOR LOOP statement.

Otherwise, lower_bound is assigned to index, the statements run, and control returns to the top of the loop, where index is compared to upper_bound. If index is less than upper_bound, index is incremented by one, the statements run again, and control returns to the top of the loop. When index is greater than upper_bound, control transfers to the statement after the FOR LOOP statement.
If REVERSE is specified:

If upper_bound is less than lower_bound, the statements do not run, and control transfers to the statement after the FOR LOOP statement.

Otherwise, upper_bound is assigned to index, the statements run, and control returns to the top of the loop, where index is compared to lower_bound. If index is greater than lower_bound, index is decremented by one, the statements run again, and control returns to the top of the loop. When index is less than lower_bound, control transfers to the statement after the FOR LOOP statement.

label

A label that identifies for_loop_statement (see "statement ::=" and "label"). CONTINUE, EXIT, and GOTO statements can reference this label.

Labels improve readability, especially when LOOP statements are nested, but only if you ensure that the label in the END LOOP statement matches a label at the beginning of the same LOOP statement (the compiler does not check).

Examples

Example 4-15, "FOR LOOP Statements"
Example 4-16, "Reverse FOR LOOP Statements"
Example 4-17, "Simulating STEP Clause in FOR LOOP Statement"
Example 4-19, "Outside Statement References FOR LOOP Statement Index"
Example 4-20, "FOR LOOP Statement Index with Same Name as Variable"
Example 4-21, "FOR LOOP Statement References Variable with Same Name as Index"
Example 4-22, "Nested FOR LOOP Statements with Same Index Name"
Example 4-23, "FOR LOOP Statement Bounds"
Example 4-24, "Specifying FOR LOOP Statement Bounds at Run Time"

Related Topics

In this chapter:

In other chapters:

"FOR LOOP Statement"