数据库时间函数
SELECT NOW();
SELECT DAY (NOW());
SELECT DATE (NOW());
SELECT TIME (NOW());
SELECT YEAR (NOW());
SELECT MONTH (NOW());
SELECT CURRENT_DATE();
SELECT CURRENT_TIME();
SELECT CURRENT_TIMESTAMP();
SELECT ADDTIME('14:23:12','01:02:01');
SELECT DATE_ADD(NOW(),INTERVAL 1 DAY);
SELECT DATE_ADD(NOW(),INTERVAL 1 MONTH);
SELECT DATE_SUB(NOW(),INTERVAL 1 DAY);
SELECT DATE_SUB(NOW(),INTERVAL 1 MONTH);
SELECT DATEDIFF('2019-07-22','2019-05-05');