Oracle中TO_NUMBER()函数的使用

TO_NUMBER(converted_str, format, nls_parameters)

SELECT TO_NUMBER('1234.56') FROM dual;  -- 1234.56

SELECT TO_NUMBER('$1,234.56', '$9,999.99') FROM dual;  -- 1234.56

-- 1234.56 (将逗号识别为小数点，点识别为千位分隔符)
SELECT TO_NUMBER('1.234,56', '9G999D99', 'NLS_NUMERIC_CHARACTERS='',.''') 
FROM dual;

-- 进制转换:16进制转换为10进制
SELECT TO_NUMBER('f','xx') FROM dual;     -- 15
SELECT TO_NUMBER('19f','xxx') FROM dual;  -- 415

-- 报错
SELECT TO_NUMBER('$12345.678', '$99999.99') FROM dual;
-- 12345.678
SELECT TO_NUMBER('$12345.678', '$99999.999') FROM dual;

-- 年
SELECT TO_NUMBER(TO_CHAR(sysdate,'yyyy')) FROM dual;  
-- 月
SELECT TO_NUMBER(TO_CHAR(sysdate,'mm')) FROM dual;    
-- 日
SELECT TO_NUMBER(TO_CHAR(sysdate,'dd')) FROM dual;    
-- 时(24小时制)
SELECT TO_NUMBER(TO_CHAR(sysdate,'hh24')) FROM dual;  
-- 分
SELECT TO_NUMBER(TO_CHAR(sysdate,'mi')) FROM dual; 
-- 秒
SELECT TO_NUMBER(TO_CHAR(sysdate,'ss')) FROM dual;