1、获取当前日期函数

        CURDATE()  

        CURRENT_DATE()

        函数获取当前日期，将当前日期按照'YYYY-MM-DD' 或 YYYYMMDD 格式返回

mysql> SELECT CURDATE(), CURRENT_DATE(), CURDATE()+0;
+------------+----------------+-------------+
| CURDATE()  | CURRENT_DATE() | CURDATE()+0 |
+------------+----------------+-------------+
| 2021-12-04 | 2021-12-04     |    20211204 |
+------------+----------------+-------------+

2、获取当前时间

        CURTIME() 和

        CURRENT_TIME()        

        函数获取当前时间，将当前时间以'HH:MM:SS' 或 HHMMSS的格式返回

mysql> SELECT CURTIME(), CURRENT_TIME(), CURTIME()+0;
+-----------+----------------+-------------+
| CURTIME() | CURRENT_TIME() | CURTIME()+0 |
+-----------+----------------+-------------+
| 18:17:35  | 18:17:35       |      181735 |
+-----------+----------------+-------------+

3、获取当前日期加时间

        NOW();
        SYSDATE();
        LOCALTIME();
        CURRENT_TIMESTAMP();
        这4个函数都可以返回当前日期和时间。

mysql> SELECT NOW(),SYSDATE(),LOCALTIME(),CURRENT_TIMESTAMP();
+---------------------+---------------------+---------------------+---------------------+
| NOW()               | SYSDATE()           | LOCALTIME()         | CURRENT_TIMESTAMP() |
+---------------------+---------------------+---------------------+---------------------+
| 2021-12-04 18:22:42 | 2021-12-04 18:22:42 | 2021-12-04 18:22:42 | 2021-12-04 18:22:42 |
+---------------------+---------------------+---------------------+---------------------+