oracle goto语句介绍
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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 primeBEGIN 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 NULLEND;/
3、使用goto分出一个环绕块:
-- example with GOTO statementDECLARE 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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