Oracle中INSTR和SUBSTR的用法

Oracle中INSTR和SUBSTR的用法

Oracle中INSTR的用法：

INSTR方法的格式為

INSTR(源字元串, 要查找的字元串, 從第幾個字元開始, 要找到第幾個比對的序号)

傳回找到的位置，如果找不到則傳回0.

例如：INSTR('CORPORATE FLOOR','OR', 3, 2)中，源字元串為'CORPORATE FLOOR', 在字元串中查找'OR'，從第三個字元位置開始查找"OR"，取第三個字後第2個比對項的位置。

預設查找順序為從左到右。當起始位置為負數的時候，從右邊開始查找。

是以SELECT INSTR('CORPORATE FLOOR', 'OR', -1, 1) "aaa" FROM DUAL的顯示結果是

Instring

——————

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oracle的substr函數的用法：

 取得字元串中指定起始位置和長度的字元串   substr( string, start_position, [ length ] )

 如:

     substr('This is a test', 6, 2)     would return 'is'

     substr('This is a test', 6)     would return 'is a test'

     substr('TechOnTheNet', -3, 3)     would return 'Net'

     substr('TechOnTheNet', -6, 3)     would return 'The'

select substr('Thisisatest', -4, 2) value from dual

綜合應用：

SELECT INSTR('CORPORATE FLOOR', 'OR', -1, 1) "Instring" FROM DUAL

--INSTR(源字元串, 目标字元串, 起始位置, 比對序号)

SELECT INSTR('CORPORATE FLOOR','OR', 3, 2) "Instring" FROM DUAL

SELECT INSTR('32.8,63.5',',', 1, 1) "Instring" FROM DUAL

SELECT SUBSTR('32.8,63.5',INSTR('32.8,63.5',',', 1, 1)+1) "INSTRING" FROM DUAL

SELECT SUBSTR('32.8,63.5',1,INSTR('32.8,63.5',',', 1, 1)-1) "INSTRING" FROM DUAL

-- CREATED ON 2008-9-26 BY ADMINISTRATOR

DECLARE

  -- LOCAL VARIABLES HERE

  T   VARCHAR2(2000);

  S   VARCHAR2(2000);

  NUM INTEGER;

  I   INTEGER;

  POS INTEGER;

BEGIN

  -- TEST STATEMENTS HERE

  T := '12.3,23.0;45.6,54.2;32.8,63.5;';

  SELECT LENGTH(T) - LENGTH(REPLACE(T, ';', '')) INTO NUM FROM DUAL;

  DBMS_OUTPUT.PUT_LINE('NUM:' || NUM);

  POS := 0;

  FOR I IN 1 .. NUM LOOP

    DBMS_OUTPUT.PUT_LINE('I:' || I);

    DBMS_OUTPUT.PUT_LINE('POS:' || POS);

    DBMS_OUTPUT.PUT_LINE('==:' || INSTR(T, ';', 1, I));

    DBMS_OUTPUT.PUT_LINE('INSTR:' || SUBSTR(T, POS + 1, INSTR(T, ';', 1, I) - 1));

    POS := INSTR(T, ';', 1, I);

  END LOOP;

END;

-- Created on 2008-9-26 by ADMINISTRATOR

declare

  -- Local variables here

  i integer;

  T      VARCHAR2(2000);

  S      VARCHAR2(2000);

begin

  -- Test statements here

    --曆史狀态

  T := '12.3,23.0;45.6,54.2;32.8,63.5;';

  IF (T IS NOT NULL) AND (LENGTH(T) > 0) THEN

    --T := T || ',';

    WHILE LENGTH(T) > 0 LOOP

      --ISTATUSID := 0;

      S         := TRIM(SUBSTR(T, 1, INSTR(T, ';') - 1));

      IF LENGTH(S) > 0 THEN

         DBMS_OUTPUT.PUT_LINE('LAT:'||SUBSTR('32.8,63.5',1,INSTR('32.8,63.5',',', 1, 1)-1));

         DBMS_OUTPUT.PUT_LINE('LON:'||SUBSTR('32.8,63.5',INSTR('32.8,63.5',',', 1, 1)+1));

        -- COMMIT;

      END IF;

      T := SUBSTR(T, INSTR(T, ';') + 1);

    END LOOP;

  END IF; 

end;