Oracle中将毫秒数转换为timestamp类型的两种方法
在许多场景中,开发人员习惯用1970-01-01 00:00:00.000以来的毫秒数来表示具体的时间,这样可以将数据以NUMBER类型存储到数据库中
在许多场景中,开发人员习惯用1970-01-01 00:00:00.000以来的毫秒数来表示具体的时间,这样可以将数据以NUMBER类型存储到数据库中,在某些时候方便比较,同样,有些时候我们需要把这种毫秒数转换成标准的TIMESTAMP类型,现在总结了两种实现方法:
方法一:
SELECT TO_TIMESTAMP('1970-01-01 00:00:00.000','yyyy-MM-dd hh24:mi:ss.ff3')+1397457489296/1000/60/60/24 FROM dual;
这种方法最简单,采用天数相加的方式,效率是比较高的,但是经测试,会丢失毫秒部分的精度,如果对毫秒级精度没有要求,,可以采用这种方式。
方法二:
这种方法比较复杂,通常需要创建一个函数,但是可以精确保留毫秒级精度!
CREATE OR REPLACE FUNCTION MILLISECONDS2TIMESTAMP(I_MILLISECONDS NUMBER)
/***************************************************************************************
名称:MILLISECONDS2TIMESTAMP
功能:将1970-01-01 00:00:00以来的毫秒数转换为对应的timestamp时间类型,精确保留毫秒级精度!
参数:I_MILLISECONDS NUMBER 待转换的毫秒数
示例:select MILLISECONDS2TIMESTAMP(1397457489296) from dual;
*************************************************************************************/
RETURN TIMESTAMP AS
V_TIMESTAMPSTR VARCHAR2(17);
BEGIN
SELECT TO_CHAR(TO_TIMESTAMP('1970-01-01', 'yyyy-MM-dd') +
TRUNC((I_MILLISECONDS -
(MOD((I_MILLISECONDS -
(MOD((I_MILLISECONDS -
MOD(I_MILLISECONDS, 1000)) / 1000,
60) * 1000 + MOD(I_MILLISECONDS, 1000))) / 1000 / 60,
60) * 60 * 1000 +
MOD((I_MILLISECONDS - MOD(I_MILLISECONDS, 1000)) / 1000,
60) * 1000 + MOD(I_MILLISECONDS, 1000))) / 1000 / 60 / 60 / 24),
'yyyyMMdd') ||--日期
LPAD(MOD((I_MILLISECONDS -
(MOD((I_MILLISECONDS -
(MOD((I_MILLISECONDS - MOD(I_MILLISECONDS, 1000)) / 1000,
60) * 1000 + MOD(I_MILLISECONDS, 1000))) / 1000 / 60,
60) * 60 * 1000 +
MOD((I_MILLISECONDS - MOD(I_MILLISECONDS, 1000)) / 1000,
60) * 1000 + MOD(I_MILLISECONDS, 1000))) / 1000 / 60 / 60,
24),
2,
0) || --小时
LPAD(MOD((I_MILLISECONDS -
(MOD((I_MILLISECONDS - MOD(I_MILLISECONDS, 1000)) / 1000,
60) * 1000 + MOD(I_MILLISECONDS, 1000))) / 1000 / 60,
60),
2,
0) || --分钟
LPAD(MOD((I_MILLISECONDS - MOD(I_MILLISECONDS, 1000)) / 1000, 60),
2,
0) || --秒
LPAD(MOD(I_MILLISECONDS, 1000), 3, 0) --毫秒
INTO V_TIMESTAMPSTR
FROM DUAL;
RETURN TO_TIMESTAMP(V_TIMESTAMPSTR, 'yyyyMMddhh24missff3');
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END;
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