oracle goto语句介绍
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http://blog.csdn.net/indexman/article/details/19050419
以下内容来自oracle plsql user guide.
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一 定义:
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:
- 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';
- <<print_now>>
- dbms_output.put_line(to_char(n) || p);
- END;
- /
2、使用null避免报错:
- DECLARE
- done BOOLEAN;
- BEGIN
- FOR i IN 1 .. 50 LOOP
- IF done THEN
- GOTO end_loop;
- END IF;
- <<end_loop>> -- 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:
- -- example with GOTO statement
- DECLARE
- v_last_name VARCHAR2(25);
- v_emp_id NUMBER(6) := 120;
- BEGIN
- <<get_name>>
- 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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