oraclegoto语句介绍

TheOraclePL/SQL GOTO statement is a sequential control structure available in Oracle. The GOTO statement immediately transfers program control (called branching) unconditionally to a named statement label or block label. The statement or

The Oracle PL/SQL GOTO statement is a sequential control structure available in Oracle. The GOTO statement immediately transfers program control (called "branching") unconditionally to a named statement label or block label. The statement or label name must be unique in the block.

属于plsql控制语句，用于程序控制非条件跳至指定标签<>。不易控制和维护，慎用！

二 例子：

1、简单GOTO 语句，判断数字是否为质数：

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DECLARE

p VARCHAR2(30);

n PLS_INTEGER := 37; -- test any integer > 2 for prime

BEGIN

FOR j IN 2 .. round(sqrt(n)) LOOP

IF n MOD j = 0 THEN

-- test for prime

p := ' is not a prime number'; -- not a prime number

GOTO print_now;

END IF;

END LOOP;

p := ' is a prime number';

<>

dbms_output.put_line(to_char(n) || p);

END;

/

2、使用null避免报错：

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DECLARE

done BOOLEAN;

BEGIN

FOR i IN 1 .. 50 LOOP

IF done THEN

GOTO end_loop;

END IF;

<> -- not allowed unless an executable statement follows

NULL; -- add NULL statement to avoid error

END LOOP; -- raises an error without the previous NULL

END;

/

3、使用goto分出一个环绕块：

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-- example with GOTO statement

DECLARE

v_last_name VARCHAR2(25);

v_emp_id NUMBER(6) := 120;

BEGIN

<>

SELECT last_name

INTO v_last_name

FROM employees

WHERE employee_id = v_emp_id;

BEGIN

dbms_output.put_line(v_last_name);

v_emp_id := v_emp_id + 5;

IF v_emp_id < 120 THEN

GOTO get_name; -- branch to enclosing block

END IF;

END;

END;

/

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