mysql 时间

显示当前时间：

mysql> select now();
+---------------------+
| now()               |
+---------------------+
| -- :: |
+---------------------+
 row in set (0.00 sec)

mysql> SELECT CURRENT_TIMESTAMP;
+---------------------+
| CURRENT_TIMESTAMP   |
+---------------------+
| -- :: |
+---------------------+
 row in set (0.00 sec)

以秒形式显示当前时间：

mysql> select UNIX_TIMESTAMP();
+------------------+
| UNIX_TIMESTAMP() |
+------------------+
|        |
+------------------+
 row in set (0.00 sec)

精确到毫秒：

mysql> SELECT ROUND(UNIX_TIMESTAMP(CURTIME()) * );
+------------------------------------------+
| ROUND(UNIX_TIMESTAMP(CURTIME()) * ) |
+------------------------------------------+
|                             |
+------------------------------------------+
 row in set (0.02 sec)

mysql在5.6.4版本之前会将秒之后的时间截取掉，也就是最高精度只到秒。5.6.4及之后的版本支持到微秒（2010-12-10 14:12:09.019473，小数点后6位）。不过创建表时需要指定精度，指定小数点后存储几位：

CREATE TABLE t1 (t TIME(), dt DATETIME());

例如：

mysql> CREATE TABLE fractest( c1 TIME(), c2 DATETIME(), c3 TIMESTAMP() );
Query OK,  rows affected (0.61 sec)

mysql> INSERT INTO fractest VALUES ('17:51:04.777', '2016-10-10 17:51:04.777', '2016-10-10 17:51:04.777');
Query OK,  row affected (0.05 sec)

mysql> SELECT * FROM fractest;
+-------------+------------------------+------------------------+
| c1          | c2                     | c3                     |
+-------------+------------------------+------------------------+
| ::04.78 | -- ::04.78 | -- ::04.78 |
+-------------+------------------------+------------------------+
 row in set (0.00 sec)