PostgreSQL实现dateadd函数

Sql代码

CREATE OR REPLACE FUNCTION timeadd(difftype character varying, incrementvalue integer, inputdate timestamp with time zone)

RETURNS timestamp without time zone AS

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DECLARE

YEAR_CONST Char(15) := 'year';

MONTH_CONST Char(15) := 'month';

WEEK_CONST Char(15) := 'week';

DAY_CONST Char(15) := 'day';

HOUR_CONST Char(15) := 'hour';

MIN_CONST Char(15) :='mi';

SECOND_CONST Char(15) :='ss';

dateTemp timestamp;

intervals interval;

BEGIN

IF lower($1) = lower(YEAR_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' year' as interval) into intervals; www.zzzyk.com

ELSEIF lower($1) = lower(MONTH_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' months' as interval) into intervals;

ELSEIF lower($1) = lower(WEEK_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' week' as interval) into intervals;

ELSEIF lower($1) = lower(DAY_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' day' as interval) into intervals;

ELSEIF lower($1) = lower(HOUR_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' hour' as interval) into intervals;

ELSEIF lower($1) = lower(MIN_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' minute' as interval) into intervals;

ELSEIF lower($1) = lower(SECOND_CONST) THEN

select cast(cast(incrementvalue as character varying) || ' second' as interval) into intervals;

END IF;

dateTemp:= inputdate + intervals;

RETURN dateTemp;

END;

$BODY$

LANGUAGE 'plpgsql' VOLATILE;

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------------------------------------------- API ------------------------------------------------------------

功能：类似于Sybase语法中的dateadd函数，用于时间加减相应的时间段

参数：

$1 时间运算格式，分为：ss（秒）,mi（分钟）,hour（小时）,day（天）,week（周）,month（月）,year（年）

$2 时间运算间隔，整型，正负均可

$3 本地时间，常用now()代替

范例：

Sql代码

select timeadd('day',-1,now())