用循環結構創建一個函數，該函數返回Smith作爲htimS。使用循環結構。有關Oracle應用

Question

CREATE OR REPLACE FUNCTION letter_reverse 
    (char_string IN VARCHAR2) 
    RETURN VARCHAR2 IS 
    v_rev_stg VARCHAR2 := 'htimS'; 
BEGIN 
    LOOP 
    rev_stg := SUBSTR(rev_stg, 'h',5) || SUBSTR(rev_stg, 't',4) || SUBSTR(rev_stg, 'i',3) ||SUBSTR(rev_stg, 'm',2) || SUBSTR(rev_stg, 'S',1); 
    END LOOP; 
END; 

錯誤PL/SQL在第7行：PL/SQL：語句被忽略

5. BEGIN 
6. LOOP 
7.  rev_stg := SUBSTR(rev_stg, 'h',5) || SUBSTR(rev_stg, 't',4) || SUBSTR(rev_stg, 'i',3) ||SUBSTR(rev_stg, 'm',2) || SUBSTR(rev_stg, 'S',1); 
8. END LOOP; 
9. END; 

Answer 1

如果你想要一個功能，爲什麼硬編碼的價值？一般功能可以如下。

CREATE OR REPLACE FUNCTION letter_reverse 
    (char_string IN VARCHAR2) 
    RETURN VARCHAR2 IS 
    v_rev_stg VARCHAR2(20) := NULL; 

BEGIN 
    for i in reverse 1..length(char_string) --loop through the length of string backwards. 
    LOOP 
     v_rev_stg := v_rev_stg||SUBSTR(char_string,i,1) ; -- append elements to v_rev_stg 
    END LOOP; 

    RETURN v_rev_stg; 
END; 

/

select letter_reverse('Smith') reversed FROM DUAL; 
REVERSED 
-------- 
htimS 

注：甲骨文確實有被無證一REVERSE功能。

Answer 2

爲您考慮另一種選擇：

DECLARE 
    l_string VARCHAR2 (100) := '?taerg LQS/LP t''nsI'; 
BEGIN 
    DBMS_OUTPUT.put_line (
     UTL_RAW.cast_to_varchar2 (
     UTL_RAW.reverse (UTL_RAW.cast_to_raw (l_string)))); 
END;