PostgreSQL实现dateadd函数
CREATE OR REPLACE FUNCTION timeadd(difftype character varying, incrementvalue integer, inputdate timestamp with time zone)RETURNS timestamp without time zone AS$BODY$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; 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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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：
select timeadd('day',-1,now())
页:
[1]