1、通过rpm包安装的MySQL
service mysqld restart
/etc/inint.d/mysqld start
2、从源码包安装的MySQL
// linux关闭MySQL的命令
$mysql_dir/bin/mysqladmin -uroot -p shutdown
// linux启动MySQL的命令
$mysql_dir/bin/mysqld_safe &
其中mysql_dir为MySQL的安装目录,mysqladmin和mysqld_safe位于MySQL安装目录的bin目录下。
参考文章: https://www.jb51.net/article/101531.htmmysql在进行不同类型的参数的运算时会产生隐式转换。其中,当需要把字符串转为浮点数的时,mysql从左边开始对字符串做转换处理的,转换规则如下:
数字转字符mysql> SELECT CONCAT ( CAST(1 as char) , '2') AS test
+------+
| test |
+------+
| 12 |
+------+
1 row in set (0.00 sec)
mysql> SELECT CONCAT ( Convert(1, char) , '2') AS test
+------+
| test |
+------+
| 12 |
+------+
1 row in set (0.00 sec)
字符转数字
mysql> SELECT CAST('1' as SIGNED) + 100 AS test
+------+
| test |
+------+
| 101 |
+------+
1 row in set (0.00 sec)
mysql> SELECT Convert('1' , SIGNED) + 100 AS test
+------+
| test |
+------+
| 101 |
+------+
1 row in set (0.00 sec)
欢迎分享,转载请注明来源:内存溢出
评论列表(0条)