一 定義：
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.
屬於plsql控制語句，用於程序控制非條件跳至指定標簽<<???>>。不易控制和維護，慎用！
二 例子：
1、簡單GOTO 語句，判斷數字是否為質數：
? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 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避免報錯：
? 1 2 3 4 5 6 7 8 9 10 11 12 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分出一個環繞塊：
? 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 -- 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; /----------------------
dylan presents.
