開(kāi)發(fā)中遇到過(guò)問(wèn)題就是對(duì)時(shí)間以半個(gè)小時(shí)分鐘分組，如統(tǒng)計(jì)08：00-08：30的人數(shù)，08：30-09：00的人數(shù)，貌似sql中沒(méi)有這樣的函數(shù)吧，直接從數(shù)據(jù)庫(kù)里查出來(lái)，在java里分組也太low了吧

想到方法1 自定義函數(shù)，自己實(shí)現(xiàn)時(shí)間的半個(gè)小時(shí)轉(zhuǎn)換，統(tǒng)計(jì)時(shí)調(diào)用函數(shù)

CREATE FUNCTION `date_half_hour_format`(in_date TIMESTAMP) RETURNS TIMESTAMP
BEGIN
DECLARE out_date TIMESTAMP;
DECLARE s_date VARCHAR(255);
DECLARE s_minute VARCHAR(2);
DECLARE int_minute INT;

SET s_minute = SUBSTRING(in_date, 15, 2);
SET int_minute = CAST(s_minute AS SIGNED);

IF int_minute <= 29 THEN
SET int_minute = 0;
SET s_date = CONCAT(LEFT(in_date, 14),’0′,int_minute);
ELSE
SET int_minute = 30;
SET s_date = CONCAT(LEFT(in_date, 14),int_minute);
END IF;

SET out_date = STR_TO_DATE(s_date,’%Y-%m-%d %H:%i’);

RETURN out_date;
END