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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.
Cursor FOR Loops In most cases that need an explicit cursor, you can simplify the coding by using a cursor FOR loop rather of the OPEN, FETCH, and CLOSE statements. A cursor FO
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
Entering and Exiting If you enter the executable part of an autonomous routine, the major transaction suspends. When you exit the routine, the major transaction resumes. To ex
Operator Precedence The operations within an expression are completed in a particular order depending on their precedence (priority). The table shows the default order of the op
UTL_FILE: The Package UTL_FILE permits your PL/SQL programs to read & write operating system (OS) text files. It gives a restricted version of the standard OS stream file I/O,
Data Types and Representations This explains the concept possible representation, abbreviated possrep, and explains how these can be used in conjunction with constraints to de
Example of DELETE - SQL As with UPDATE, a FOR PORTION OF clause can be specified if the target table has a defined period name, as illustrated in Example. Example: Deleting
Example of NOT EXISTS in SQL Example: Use of NOT EXISTS CREATE ASSERTION Must_be_enrolled_to_take_exam_alternative1 CHECK ( NOT EXISTS (SELECT StudentId, CourseId
Using SET TRANSACTION You use the SET TRANSACTION statement to begin the read-only or read-write transaction, start an isolation level, or assign your present transaction to a
LOB Types The large object (LOB) datatypes like BFILE, BLOB, CLOB, and NCLOB store the blocks of unstructured data (like graphic images, text, video clips, and sound waveforms)
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