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

In packages - subprograms, In Packages The Forward declarations also g...

In Packages The Forward declarations also group logically related subprograms in the package. The subprogram specifications go in the package specification, & the subprogram b

Select into statement - syntax, SELECT INTO Statement   The SELECT INT...

SELECT INTO Statement   The SELECT INTO statement retrieve data from one or more database tables, and then assigns the selected values to the variables or fields. Syntax:

Cause of indeterminacy in sql, Cause of Indeterminacy in SQL One root ...

Cause of Indeterminacy in SQL One root cause of indeterminacy in SQL lies in its implementation of comparison for equality. For certain system-defined types it is possible for

Using %type-declarations in sql, Using %TYPE The %TYPE attribute gives th...

Using %TYPE The %TYPE attribute gives the datatype of a variable or the database column. In the example below, the %TYPE gives the datatype of a variable: credit REAL(7,2); debi

Exceptions - syntax, Exceptions An exception is the runtime error or wa...

Exceptions An exception is the runtime error or warning condition that can be predefined or user-defined. The Predefined exceptions are raised implicitly through runtime system

Advantages of pl/sql, Advantages of PL/SQL The PL/SQL is a high-perform...

Advantages of PL/SQL The PL/SQL is a high-performance transaction processing, completely portable language that offers the following advantages as shown: 1) Support for SQL

Predefined exceptions, Predefined Exceptions The internal exception is ...

Predefined Exceptions The internal exception is raised implicitly whenever your PL/SQL program exceeds a system-dependent limit or violates an Oracle rule. Each & every Oracle

Update statement - syntax, UPDATE Statement   The UPDATE statement tra...

UPDATE Statement   The UPDATE statement transforms the values of the specified columns in one or more rows in the table or view. Syntax:

Effect of anonymous columns, Effect of Anonymous Columns Now, recall t...

Effect of Anonymous Columns Now, recall that a VALUES expression denotes a table with undefined column names. If an initial value is to be specified when a base table is creat

Sql pseudocolumns, SQL Pseudocolumns The PL/SQL recognizes the followin...

SQL Pseudocolumns The PL/SQL recognizes the following SQL pseudocolumns, that returns the specific data items: LEVEL, NEXTVAL, CURRVAL, ROWID, & ROWNUM. The Pseudocolumns are n

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