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

Using aggregation on nested tables - sql, Using Aggregation on Nested Table...

Using Aggregation on Nested Tables Example is the most direct translation of its counterpart in the theory book that can be obtained in SQL but it is so over-elaborate that no

Sql script to create and populate the tables, Create the four tables and po...

Create the four tables and populate them with the given data. Answer the following queries in SQL. 1. Get all part-color/part-city combinations. Note: Here and subsequently, the

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

Identifiers in pl/sql, Identifiers You use identifiers to name the PL/S...

Identifiers You use identifiers to name the PL/SQL program items and units that include constants, variables, cursors, exceptions, cursor variables, subprograms, and packages.

Effects of null in table literal, Effects of NULL in Table Literal Whe...

Effects of NULL in Table Literal When a VALUES expression appears as the source value for an SQL INSERT statement, the key word NULL can appear as a field value, such that for

Oracle 9i features, Bitmap Join Indexes - This feature will increase th...

Bitmap Join Indexes - This feature will increase the performance and detains the size and format of your databases in data Character Semantics and Globalization -This featur

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

Data types, Datatypes Every constant and variable has a datatype that s...

Datatypes Every constant and variable has a datatype that specifies the storage format, constraints, and the valid range of values. The PL/SQL gives a variety of predefined dat

Using default-declarations in sql, Using DEFAULT You can use the keyword...

Using DEFAULT You can use the keyword DEFAULT rather than that of the assignment operator to initialize the variables. For e.g. the declaration blood_type CHAR := ’O’; it can b

Multiple assignment - sql, Multiple Assignment- SQL SQL supports mult...

Multiple Assignment- SQL SQL supports multiple assignment to local variables and also applies multiple assignment semantics in SET clauses of UPDATE statements, but does not

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