计算Oracle两个TIMESTAMP相差的毫秒数

CREATE OR REPLACE FUNCTION uf_timestamp_diff(endtime in TIMESTAMP,starttime in TIMESTAMP)

RETURN INTEGER

AS

str VARCHAR2(50);

misecond INTEGER;

seconds INTEGER;

minutes INTEGER;

hours INTEGER;

days INTEGER;

BEGIN

str:=to_char(endtime-starttime);

misecond:=to_number(SUBSTR(str,INSTR(str,' ')+10,3));

seconds:=to_number(SUBSTR(str,INSTR(str,' ')+7,2));

minutes:=to_number(SUBSTR(str,INSTR(str,' ')+4,2));

hours:=to_number(SUBSTR(str,INSTR(str,' ')+1,2));

days:=to_number(SUBSTR(str,1,INSTR(str,' ')));

RETURN days*24*60*60*1000+hours*60*60*1000+minutes*60*1000+seconds*1000+misecond;

END;