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 Data Manipulation (DML) StatementsBuilt-in Scalar Functions 

WHILE …​ DO

Looping construct

Syntax
[label:]
WHILE (<condition>) DO
  <compound_statement>
Table 1. WHILE …​ DO Parameters
Argument Description

label

Optional label for LEAVE and CONTINUE.Follows the rules for identifiers.

condition

A logical condition returning TRUE, FALSE or UNKNOWN

compound_statement

A single statement, or statements wrapped in BEGIN …​ END

A WHILE statement implements the looping construct in PSQL.The statement or the block of statements will be executed as long as the condition returns TRUE.Loops can be nested to any depth.

WHILE …​ DO Examples

A procedure calculating the sum of numbers from 1 to I shows how the looping construct is used.

CREATE PROCEDURE SUM_INT (I INTEGER)
RETURNS (S INTEGER)
AS
BEGIN
  s = 0;
  WHILE (i > 0) DO
  BEGIN
    s = s + i;
    i = i - 1;
  END
END

Executing the procedure in isql:

EXECUTE PROCEDURE SUM_INT(4);

the result is:

S
==========
10
See also

[fblangref50-psql-ifthen], [fblangref50-psql-break], [fblangref50-psql-leave], [fblangref50-psql-continue], [fblangref50-psql-exit], [fblangref50-psql-forselect], [fblangref50-psql-forexec]