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

Cartesian product, Using a Join on 2 tables, select all columns and all row...

Using a Join on 2 tables, select all columns and all rows from the tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 JOIN CONTRACT ON EMPLOYEE

Execute your documentation in oracle, Using research notes and Oracle docum...

Using research notes and Oracle documentation plan and execute an upgrade of an installation of Oracle 10g to Oracle 11g release 1. To do this you must show in screen shots and wri

Sql, Write a query to find academics that are authors and that have only ev...

Write a query to find academics that are authors and that have only ever coauthored papers with authors from institutes in the same state as their own. List their academic number,

Number types in pl/sql, Number Types The Number types permit you to sto...

Number Types The Number types permit you to store the numeric data (real numbers, integers, and floating-point numbers), show quantities, and do computations. BINARY_INTEG

Joining in sql, Joining in SQL Joining IS_CALLED and IS_ENROLLED_ON in...

Joining in SQL Joining IS_CALLED and IS_ENROLLED_ON in SQL SELECT * FROM IS_CALLED NATURAL JOIN IS_ENROLLED_ON This is an example of an SQL table expression. I have been

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:

Sequential control - pl/sql, Sequential Control Dissimilar to the IF and ...

Sequential Control Dissimilar to the IF and LOOP statements, the GOTO and NULL statements are not important to the PL/SQL programming. The configuration of PL/SQL is such that th

Manipulating local collections - pl/sql, Manipulating Local Collections ...

Manipulating Local Collections Within PL/SQL, to manipulate the local collection, by using the  TABLE and CAST operators . The operands of CAST are a collection declared locally

Controlling autonomous transactions, Controlling Autonomous Transactions ...

Controlling Autonomous Transactions The first SQL statement in an autonomous routine starts a transaction. Whenever one transaction ends, the next SQL statement starts the oth

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

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