Oracle中INSTR和SUBSTR的用法

Oracle中INSTR和SUBSTR的用法

Oracle中INSTR的用法：
INSTR方法的格式爲
INSTR(源字符串, 要查找的字符串, 從第幾個字符開始, 要找到第幾個匹配的序號)
返回找到的位置，若是找不到則返回0.
例如：INSTR('CORPORATE FLOOR','OR', 3, 2)中，源字符串爲'CORPORATE FLOOR', 在字符串中查找'OR'，從第三個字符位置開始查找"OR"，取第三個字後第2個匹配項的位置。

默認查找順序爲從左到右。當起始位置爲負數的時候，從右邊開始查找。

因此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：
 取得字符串中指定起始位置和長度的字符串   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(源字符串, 目標字符串, 起始位置, 匹配序號)
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     --歷史狀態   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;