Help Center/ GaussDB/ Distributed_8.x/ Stored Procedures/ Control Statements/ GOTO Statements
Updated on 2024-06-03 GMT+08:00
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GOTO Statements

A GOTO statement unconditionally transfers the control from the current statement to a labeled statement. The GOTO statement changes the execution logic. Therefore, use this statement only when necessary. Alternatively, you can use the EXCEPTION statement to handle issues in special scenarios. To execute a GOTO statement, the labeled statement must be unique.

Syntax

Figure 1 shows the label declaration ::= statement.

Figure 1 label declaration ::

Figure 2 shows the goto statement ::= statement.

Figure 2 goto statement ::

Examples

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gaussdb=# CREATE OR REPLACE PROCEDURE GOTO_test()
AS 
DECLARE
    v1  int;
BEGIN
    v1  := 0;
        LOOP
        EXIT WHEN v1 > 100;
                v1 := v1 + 2;
                if v1 > 25 THEN
                        GOTO pos1;
                END IF;
        END LOOP;
<<pos1>>
v1 := v1 + 10;
raise info 'v1 is %. ', v1;
END;
/
CREATE PROCEDURE
gaussdb=# call GOTO_test();
INFO:  v1 is 36. 
 goto_test 
-----------

(1 row)

Constraints

Using GOTO statements has the following constraints:

  • Does not allow multiple labeled GOTO statements even if the statements are in different blocks. 
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    BEGIN
  GOTO pos1; 
  <<pos1>>
  SELECT * FROM ...
  <<pos1>>
  UPDATE t1 SET ...
END;
  • A GOTO statement cannot transfer control to the IF, CASE, or LOOP statement. 
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    BEGIN
   GOTO pos1; 
   IF valid THEN
     <<pos1>>
     SELECT * FROM ...
   END IF;
 END;
  • A GOTO statement cannot transfer control from one IF clause to another, or from one WHEN clause in the CASE statement to another. 
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    BEGIN 
   IF valid THEN
     GOTO pos1;
     SELECT * FROM ...
   ELSE
     <<pos1>>
     UPDATE t1 SET ...
   END IF;
 END;
  • Transferring control from an outer block to an inner BEGIN-END block is not supported. 
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    BEGIN
   GOTO pos1;  
   BEGIN
     <<pos1>>
     UPDATE t1 SET ...
   END;
 END;
  • Cannot transfer control from an exception handler to the current BEGIN-END block, but can transfer control to the upper-layer BEGIN-END block. 
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    BEGIN
   <<pos1>>
   UPDATE t1 SET ...
   EXCEPTION
     WHEN condition THEN
        GOTO pos1;
 END;
  • To branch to a position that does not have an executable statement, you need to add the NULL statement. 
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    DECLARE
   done  BOOLEAN;
BEGIN
   FOR i IN 1..50 LOOP
      IF done THEN
         GOTO end_loop;
      END IF;
      <<end_loop>>  -- You cannot run the GOTO statement to go here unless there is an executable statement following it.
      NULL; -- The statement added here is used to avoid errors.
   END LOOP;  -- If the previous sentence NULL does not exist, an error is reported.
END;
/
Parent topic: Control Statements