oracle的函數cast進行類型轉換用法

-- 字符串轉數字number
select cast('123.456' as number(10,2)) from dual

-- 字符串轉s數字integer
select cast('123.456' as integer) from dual

-- 數字轉字符串
select cast(123.456 as varchar2(100)) from dual

-- 字符串轉時間戳
select cast('25-1月 -19 12.49.40.123456789 下午' as timestamp) from dual

-- 時間戳轉字符串
select cast(to_timestamp(to_char(sysdate,'yyyy-mm-dd hh24:mi:ss')||'.123456789','yyyy-mm-dd hh24:mi:ss.ff') as varchar2(100)) from dual

-- 字符串轉日期
select cast('25-1月 -19' as date) from dual

-- 日期轉字符串
select cast(sysdate as varchar2(100)) from dual

一般跟在select後對查詢的字段轉換類型