MySQL: TIMESTAMP 的默认值无效

Question

我收到错误

ERROR 1067 (42000) at line 5459: Invalid default value for 'start_time'

当运行以下查询时

DROP TABLE IF EXISTS `slow_log`;
CREATE TABLE IF NOT EXISTS `slow_log` (
  `start_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `user_host` mediumtext NOT NULL,
  `query_time` time(6) NOT NULL,
  `lock_time` time(6) NOT NULL,
  `rows_sent` int(11) NOT NULL,
  `rows_examined` int(11) NOT NULL,
  `db` varchar(512) NOT NULL,
  `last_insert_id` int(11) NOT NULL,
  `insert_id` int(11) NOT NULL,
  `server_id` int(10) unsigned NOT NULL,
  `sql_text` mediumtext NOT NULL
) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='Slow log';

我正在使用 MySQL 5.7.18

$ mysql --version
mysql  Ver 14.14 Distrib 5.7.18, for osx10.10 (x86_64) using  EditLine wrapper

根据MySQL 5.7 documentation，下面的语法是

CREATE TABLE t1 (
  ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  dt DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
);

上面的 SQL 语法有什么问题？

Answer 1

尝试：

mysql> DROP TABLE IF EXISTS `slow_log`;
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE TABLE IF NOT EXISTS `slow_log` (
    ->   `start_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6)
    ->                                      ON UPDATE CURRENT_TIMESTAMP(6),
    ->   `user_host` mediumtext NOT NULL,
    ->   `query_time` time(6) NOT NULL,
    ->   `lock_time` time(6) NOT NULL,
    ->   `rows_sent` int NOT NULL,
    ->   `rows_examined` int NOT NULL,
    ->   `db` varchar(512) NOT NULL,
    ->   `last_insert_id` int NOT NULL,
    ->   `insert_id` int NOT NULL,
    ->   `server_id` int unsigned NOT NULL,
    ->   `sql_text` mediumtext NOT NULL
    -> ) ENGINE=CSV DEFAULT CHARSET=utf8 COMMENT='Slow log';
Query OK, 0 rows affected (0.00 sec)

Answer 2

有趣的是，这两个都有效：

`start_time` timestamp(6),

并且：

`start_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,

您可以使用后者——将精度说明符排除在定义之外。

但正确的方法是：

`start_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6),

如 documentation 中所述：

If a TIMESTAMP or DATETIME column definition includes an explicit fractional seconds precision value anywhere, the same value must be used throughout the column definition. This is permitted:
CREATE TABLE t1 (
  ts TIMESTAMP(6) DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6)
);
This is not permitted:
CREATE TABLE t1 (
  ts TIMESTAMP(6) DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(3)
);

MySQL: TIMESTAMP 的默认值无效

MySQL: Invalid default value for TIMESTAMP

mysql

sql

create-table

mysql-error-1067

mysql-5.7