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GOTO StatementThe 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...<>BEGINUPDATE 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:DECLAREdone BOOLEAN;BEGIN...FOR i IN 1..50 LOOPIF done THENGOTO end_loop;END IF;...<> -- illegalEND LOOP; -- not an executable statementEND;To debug the last illustration, now add the NULL statement, as shown:FOR i IN 1..50 LOOPIF done THENGOTO end_loop;END IF;...<>NULL; -- an executable statementEND LOOP;As the following illustration shows, a GOTO statement can branch to an enclosing block from the present block:DECLAREmy_ename CHAR(10);BEGIN<>SELECT ename INTO my_ename FROM emp WHERE...BEGIN...GOTO get_name; -- branch to enclosing blockEND;END;RestrictionsSome 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 clauseELSE...<>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’ THENGOTO delete_part; -- illegal branch into sub-blockEND 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) ISBEGIN...GOTO update_row; -- illegal branch out of subprogramEND;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, ...);EXCEPTIONWHEN ZERO_DIVIDE THENpe_ratio := 0;GOTO insert_row; -- illegal branch into current blockEND;Though, a GOTO statement can branch from an exception handler into the enclosing block.
UNION and OR - SQL SQL supports UNION explicitly but differently from the way it supports JOIN explicitly. As we have seen, JOIN is used exclusively within the FROM clause, su
Using the BULK COLLECT Clause The keywords BULK COLLECT specify the SQL engine to bulk-bind output collections before returning them to the PL/SQL engine. You can use these ke
How Bulk Binds Improve Performance The assigning of values to the PL/SQL variables in SQL statements is known as binding. The binding of the whole collection at once is know
Bulk Binds advantages In the Embedded Oracle RDBMS, the PL/SQL engines accept any valid PL/SQL subprogram or block. As the figure shows, the PL/SQL engine executes all procedur
Left and Right Joins LEFT OUTER JOIN can be used when you want to retrieve the data from the main table (table1) even if there is no match in other tables (table_2, table_3...
Scope and Visibility The References to an identifier are resolved according to its visibility and scope. The scope of an identifier is that area of a program unit (subprogram, b
Example of WHEN or THEN Constraints A concrete example showing how SQL supports WHEN/THEN constraints CREATE TABLE SAL_HISTORY (EmpNo CHAR (6), Salary INTEGER NOT NULL,
Using Cursor Attributes: Every cursor has 4 attributes: %NOTFOUND, %FOUND, %ISOPEN, and %ROWCOUNT. If appended to the cursor name, they return the helpful information about
Raise_application_error - procedure of package DBMS_STANDARD , allows to issue an user_defined error messages by stored sub-program or database trigger.
Using COMMIT The COMMIT statements end the present transaction and make permanent any changes made during that transaction. Till you commit the changes, other users cannot acc
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