Goto statement - sequential control, PL-SQL Programming

Assignment Help:

GOTO Statement

The GOTO statement branches to a label unconditionally. The label must be exclusive within its scope and should precede an executable statement or a PL/SQL block. If executed, the GOTO statement transfers control to the labeled statement or block. In the following illustration, you go to an executable statement farther down in a series of statements:


BEGIN
...
GOTO insert_row;
...
<>
INSERT INTO emp VALUES...
END;


In the next illustration, you go to a PL/SQL block farther up in a series of statements:


BEGIN
...
<>
BEGIN
UPDATE emp SET ...
...
END;
...
GOTO update_row;
...
END;


The label end_loop in the example below is illegal as it does not precede an executable statement:


DECLARE
done BOOLEAN;
BEGIN
...
FOR i IN 1..50 LOOP
IF done THEN
GOTO end_loop;
END IF;
...

<> -- illegal
END LOOP; -- not an executable statement
END;


To debug the last illustration, now add the NULL statement, as shown:

FOR i IN 1..50 LOOP
IF done THEN
GOTO end_loop;
END IF;
...
<>
NULL; -- an executable statement
END LOOP;


As the following illustration shows, a GOTO statement can branch to an enclosing block from the present block:

DECLARE
my_ename CHAR(10);
BEGIN
<>
SELECT ename INTO my_ename FROM emp WHERE...
BEGIN
...
GOTO get_name; -- branch to enclosing block
END;
END;



Restrictions

Some likely destinations of a GOTO statement are illegal. Particularly, a GOTO statement cannot branch into an IF statement, LOOP statement, or sub-block. For illustration, the following GOTO statement is illegal:



BEGIN
...
GOTO update_row; -- illegal branch into IF statement
...
IF valid THEN
...
<>
UPDATE emp SET...
END IF;
END;

A GOTO statement also cannot branch from one IF statement clause to another, as the following illustration shows:


BEGIN
...
IF valid THEN
...
GOTO update_row; -- illegal branch into ELSE clause
ELSE
...
<>
UPDATE emp SET...
END IF;
END;


The next illustration shows that a GOTO statement cannot branch from an enclose block into a sub-block:


BEGIN
...
IF status = ’OBSOLETE’ THEN
GOTO delete_part; -- illegal branch into sub-block
END IF;
...

BEGIN
...
<>
DELETE FROM parts WHERE...
END;
END;


A GOTO statement also cannot branch out of a subprogram, as the following illustration shows:


DECLARE
...
PROCEDURE compute_bonus (emp_id NUMBER) IS
BEGIN
...
GOTO update_row; -- illegal branch out of subprogram
END;
BEGIN
...
<>
UPDATE emp SET...
END;


Finally, the GOTO statement cannot branch from an exception handler into the present block. For illustration, the following GOTO statement is illegal:


DECLARE
...
pe_ratio REAL;
BEGIN
...
SELECT price / NVL(earnings, 0) INTO pe_ratio FROM ...
<>
INSERT INTO stats VALUES (pe_ratio, ...);
EXCEPTION
WHEN ZERO_DIVIDE THEN
pe_ratio := 0;
GOTO insert_row; -- illegal branch into current block
END;


Though, a GOTO statement can branch from an exception handler into the enclosing block.


Related Discussions:- Goto statement - sequential control

Rollback behavior - bulk bind performance improvement, Rollback Behavior ...

Rollback Behavior When a FORALL statement fails, the database changes are rolled back to an implicit savepoint marked before each of the SQL statement execution. The Changes t

Pl/sql assignment, 1. a. Write a trigger that fires when a part's price...

1. a. Write a trigger that fires when a part's price is updated. The trigger will write a record into a table called PriceUpdates. The record should contain the information of

Merge two data sources to sql azure database, Project Description: I hav...

Project Description: I have two types of data sources. One that is a list in SharePoint and another that is an access desktop database. The access desktop database is fairly com

Exceptions are raised - Using Raise statement, How Exceptions Are Raised ...

How Exceptions Are Raised By the run-time system, the internal exceptions are raised implicitly as are user-defined exceptions that you have related with an Oracle error number

Triggers, At times, customers make mistakes in submitting their orders and ...

At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a trigger that automatically updates the stock level of all pr

Cursor variables as parameters, Cursor Variables As Parameters You can...

Cursor Variables As Parameters You can declare the cursor variables as the formal parameters of the functions and procedures. In the illustration below, you define the REF CUR

Parameter and keyword description - procedures, Parameter and Keyword Descr...

Parameter and Keyword Description: procedure_name The user-defined procedure is declared by this construct. parameter_name: This identifies the formal parameter t

%type - cursors, %TYPE: This attribute gives the datatype of a formerly...

%TYPE: This attribute gives the datatype of a formerly declared collection, cursor variable, object, field, record, database column, or variable. Datatype: This is simply

Keyword and parameter description in pl sql, Keyword and Parameter Descript...

Keyword and Parameter Description: label_name: This is an undeclared identifier which optionally labels the PL/SQL block. When used, label_name should be enclosed by the do

Write a pl/sql anonymous block that accepts an employee id, Based on the EM...

Based on the EMPLOYEE table created in Assignment #1, write a PL/SQL anonymous block that accepts an employee ID from the user input and finds whether the employee ID is in the EMP

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd