最近在捣鼓wordpress主从同步的时候（ubuntu 16.04配置MySQL主从同步），需要把wp_comments的数据库引擎从MyISAM切换到INNODB（MyISAM不支持主从同步）。
在执行
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$ mysql -u root -p -e "use wordpress; ALTER TABLE wp_comments ENGINE=INNODB;" |
的时候报告错误：
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Invalid default value for 'comment_date' |
原因出在类似这样的建表语句
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DROP TABLE IF EXISTS `wp_comments`; CREATE TABLE `wp_comments` ( `comment_ID` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT, `comment_post_ID` bigint(20) UNSIGNED NOT NULL DEFAULT 0, `comment_author` tinytext CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL, `comment_author_email` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '', `comment_author_url` varchar(200) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '', `comment_author_IP` varchar(100) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '', `comment_date` datetime(0) NOT NULL DEFAULT '0000-00-00 00:00:00', `comment_date_gmt` datetime(0) NOT NULL DEFAULT '0000-00-00 00:00:00', `comment_content` text CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL, `comment_karma` int(11) NOT NULL DEFAULT 0, `comment_approved` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '1', `comment_agent` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '', `comment_type` varchar(20) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_520_ci NOT NULL DEFAULT '', `comment_parent` bigint(20) UNSIGNED NOT NULL DEFAULT 0, `user_id` bigint(20) UNSIGNED NOT NULL DEFAULT 0, PRIMARY KEY (`comment_ID`) USING BTREE, INDEX `comment_post_ID`(`comment_post_ID`) USING BTREE, INDEX `comment_approved_date_gmt`(`comment_approved`, `comment_date_gmt`) USING BTREE, INDEX `comment_date_gmt`(`comment_date_gmt`) USING BTREE, INDEX `comment_parent`(`comment_parent`) USING BTREE, INDEX `comment_author_email`(`comment_author_email`(10)) USING BTREE ) ENGINE = MyISAM AUTO_INCREMENT = 35 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_520_ci ROW_FORMAT = Dynamic; |
这种报错多是mysql升级到5.7而引起的默认值不兼容的问题。看看你的字段名是什么，我的是时间字段，类型是datetime。想到可能是类型的默认值被限制了，查看sql_mode。果然：NO_ZERO_IN_DATE,NO_ZERO_DATE这两个参数限制时间不能为0。
可以使用如下语句查看建表命令：
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$ mysql -u root -p -e "use wordpress;show create table wp_comments\G;“ |
注意上面的
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`comment_date` datetime(0) NOT NULL DEFAULT '0000-00-00 00:00:00', `comment_date_gmt` datetime(0) NOT NULL DEFAULT '0000-00-00 00:00:00', |
这两句受到NO_ZERO_IN_DATE,NO_ZERO_DATE的影响。
查看 sql_mode
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mysql> show variables like 'sql_mode'; +---------------+-------------------------------------------------------------------------------------------------------------------------------------------+ | Variable_name | Value | +---------------+-------------------------------------------------------------------------------------------------------------------------------------------+ | sql_mode | ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION | +---------------+-------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) mysql> |
临时修改：
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mysql> set session -> sql_mode='ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'; Query OK, 0 rows affected, 1 warning (0.00 sec) mysql> |
永久修改：
修改配置文件
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$ sudo vim /etc/mysql/mysql.conf.d/mysqld.cnf |
在[mysqld]下面添加如下列：
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sql_mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |