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, when a statement inside the loop transfers control outside the loop, or when an exception is raised.

Topics:

• Syntax

• Semantics

• Examples

• Related Topics

Syntax

for_loop_statement ::=

Description of the illustration for_loop_statement.gif

See statement ::=.

Semantics

index_name

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

[ REVERSE ] lower_bound .. upper_bound

The 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 the syntax diagram statement ::= and the description of 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 at the end of the LOOP statement matches one of the labels at the beginning of the same statement (the compiler does not check).

Examples

• Example 4-15, "FOR LOOP Statements"

• Example 4-16, "Reverse FOR LOOP Statements"

• Example 4-22, "Several Types of FOR LOOP Bounds"

• Example 4-23, "Changing the Increment of the Counter in a FOR LOOP Statement"

• Example 4-24, "Specifying a LOOP Range at Run Time"

• Example 4-25, "FOR LOOP with Lower Bound > Upper Bound"

• Example 4-18, "Statement Outside FOR LOOP Tries to Reference Index"

• Example 4-19, "FOR LOOP Index with Same Name as Declared Variable"

• Example 4-20, "FOR LOOP References Declared Variable with Same Name as Index"

• Example 4-21, "Nested FOR LOOP Statements with Same Index Name"

• Example 4-26, "EXIT in FOR LOOP"

• Example 4-27, "EXIT with Label in FOR LOOP"

Related Topics

In this chapter:

• "Basic LOOP Statement"

• "CONTINUE Statement"

• "Cursor FOR LOOP Statement"

• "EXIT Statement"

• "FETCH Statement"

• "FORALL Statement"

• "OPEN Statement"

• "WHILE LOOP Statement"

In other chapters:

• "FOR LOOP Statement"