由于自考的实践考核要求有需要用到 mysql 进行考核，故记录一下在 mac 环境下试手的笔记。

初始环境

首先在 mysql 官网中下载你想要的版本。可以直接下载 dmg 安装包，按照安装指示一步一步安装，并设置 mysql 的密码。

下载完毕后，一般情况下直接通过命令行使用 mysql 命令会找不到对应的命令：

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➜  ~ mysql -v
zsh: command not found: mysql

因此需要对当前的命令行工具配置对应的环境变量，比如笔者使用的是 zsh，则打开 ~/.zshrc 文件添加以下配置:

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export PATH=${PATH}:/usr/local/mysql/bin/

若使用 bash 的用户同理，直接在 ~/.bashrc 添加相同代码。添加完毕后通过 source 命令重新加载对应的环境变量: source ~/.zshrc

接着就可以在命令行直接使用 mysql 了。输入 mysql -u root -p 登录 mysql，密码是在安装阶段时设置的密码。

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➜  ~ mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 8.0.29 MySQL Community Server - GPL

Copyright (c) 2000, 2022, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

数据库操作

DATABASE 可以不区分大小写，但只能要么全小写，要么全大写。一般会将这些参数用大写写出。

创建数据库

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mysql> CREATE DATABASE DANNY_DATABASE;
Query OK, 1 row affected (0.01 sec)

查看现有的数据库

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mysql> SHOW DATABASES;
+
| Database                   |
+
| information_schema         |
| DANNY_DATABASE             |
| mysql                      |
| performance_schema         |
| sys                        |
+
6 rows in set (0.00 sec)

切换到指定数据库

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mysql> USE DANNY_DATABASE

数据库的查看与删除

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mysql> CREATE DATABASE DANNY_DATABASE_WAIT_DELETE;
Query OK, 1 row affected (0.01 sec)

mysql> SHOW DATABASES;
+
| Database                   |
+
| information_schema         |
| DANNY_DATABASE             |
| DANNY_DATABASE_WAIT_DELETE |
| mysql                      |
| performance_schema         |
| sys                        |
+
6 rows in set (0.00 sec)


mysql> DROP DATABASE DANNY_DATABASE_WAIT_DELETE;
Query OK, 0 rows affected (0.02 sec)

mysql> SHOW DATABASES;
+
| Database           |
+
| information_schema |
| DANNY_DATABASE     |
| mysql              |
| performance_schema |
| sys                |
+
5 rows in set (0.00 sec)

查看当前使用的数据库

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mysql> SELECT DATABASE();
+
| DATABASE()     |
+
| null           |
+
1 row in set (0.00 sec)


use DANNY_DATABASE;

mysql> SELECT DATABASE();
+
| DATABASE()     |
+
| danny_database |
+
1 row in set (0.00 sec)

数据表操作

创建数据表

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mysql> CREATE TABLE IF NOT EXISTS customers(
    ->   cust_id INT NOT NULL AUTO_INCREMENT,
    ->   cust_name CHAR(50) NOT NULL,
    ->   cust_sex CHAR(1) NOT NULL DEFAULT 0,
    ->   cust_address CHAR(50) NULL,
    ->   cust_contact CHAR(50) NULL,
    ->   PRIMARY KEY(cust_id)
    -> );
Query OK, 0 rows affected (0.11 sec)

其中 IF NOT EXISTS 参数是可选的，它的意思为若 customers 表不存在则创建它。

查看数据表与表列

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mysql> SHOW TABLES;
+
| Tables_in_danny_database |
+
| customers                |
+
1 rows in set (0.00 sec)



mysql> SHOW COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default   | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL      | auto_increment |
| cust_name    | char(50)    | NO   |     | NULL      |                |
| cust_sex     | char(1)     | NO   |     | 0         |                |
| cust_address | char(50)    | YES  |     | NULL      |                |
| cust_contact | char(50)    | YES  |     | NULL      |                |
+
5 rows in set (0.00 sec)

删除数据表

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mysql> CREATE TABLE IF NOT EXISTS customers_1(
    ->   cust_id INT NOT NULL AUTO_INCREMENT,
    ->   cust_name CHAR(50) NOT NULL,
    ->   cust_sex CHAR(1) NOT NULL DEFAULT 0,
    ->   cust_address CHAR(50) NULL,
    ->   cust_contact CHAR(50) NULL,
    ->   PRIMARY KEY(cust_id)
    -> );
Query OK, 0 rows affected (0.11 sec)


mysql> SHOW tables;
+
| Tables_in_danny_database |
+
| customers                |
| customers_1              |
+
2 rows in set (0.00 sec)


mysql> DROP TABLES customers_1;
Query OK, 0 rows affected (0.02 sec)

mysql> SHOW tables;
+
| Tables_in_danny_database |
+
| customers                |
+
1 row in set (0.00 sec)

数据表添加新列

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mysql> alter TABLE customers
    -> ADD COLUMN cust_city char(10) NOT NULL DEFAULT 'guangzhou' AFTER cust_sex;
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0


mysql> SHOW COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default   | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL      | auto_increment |
| cust_name    | char(50)    | NO   |     | NULL      |                |
| cust_sex     | char(1)     | NO   |     | 0         |                |
| cust_city    | char(10)    | NO   |     | guangzhou |                |
| cust_address | char(50)    | YES  |     | NULL      |                |
| cust_contact | char(50)    | YES  |     | NULL      |                |
+
6 rows in set (0.00 sec)

数据表修改表列

修改整列: 将列名 cust_sex 修改 sex，并修改默认值

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mysql> alter TABLE customers
    -> CHANGE COLUMN cust_sex sex char(1) NULL DEFAULT 'M';
Query OK, 0 rows affected (0.04 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default   | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL      | auto_increment |
| cust_name    | char(50)    | YES  |     | NULL      |                |
| sex          | char(1)     | YES  |     | M         |                |
| cust_city    | char(10)    | NO   |     | guangzhou |                |
| cust_address | char(50)    | YES  |     | NULL      |                |
| cust_contact | char(50)    | YES  |     | NULL      |                |
+
6 rows in set (0.00 sec)

仅修改列的类型

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mysql> ALTER TABLE customers
    -> MODIFY COLUMN cust_address varchar(50);
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default   | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL      | auto_increment |
| cust_name    | char(50)    | YES  |     | NULL      |                |
| sex          | char(1)     | YES  |     | M         |                |
| cust_city    | char(10)    | NO   |     | guangzhou |                |
| cust_address | varchar(50) | YES  |     | NULL      |                |
| cust_contact | char(50)    | YES  |     | NULL      |                |
+
6 rows in set (0.00 sec)

修改指定列的指定字段

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mysql> ALTER TABLE customers
    -> ALTER COLUMN cust_city SET DEFAULT 'shenzhen';
Query OK, 0 rows affected (0.03 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default  | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL     | auto_increment |
| cust_name    | char(50)    | YES  |     | NULL     |                |
| sex          | char(1)     | YES  |     | M        |                |
| cust_city    | char(10)    | NO   |     | shenzhen |                |
| cust_address | varchar(50) | YES  |     | NULL     |                |
| cust_contact | char(50)    | YES  |     | NULL     |                |
+
6 rows in set (0.00 sec)

移除数据表列： 移除 cust_contact 数据表项

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mysql> ALTER TABLE danny_database.customers
    -> DROP COLUMN cust_contact;
Query OK, 0 rows affected (0.04 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> SHOW COLUMNS from customers;
+
| Field        | Type        | Null | Key | Default  | Extra          |
+
| cust_id      | int(11)     | NO   | PRI | NULL     | auto_increment |
| cust_name    | char(50)    | YES  |     | NULL     |                |
| sex          | char(1)     | YES  |     | M        |                |
| cust_city    | char(10)    | NO   |     | shenzhen |                |
| cust_address | varchar(50) | YES  |     | NULL     |                |
+
5 rows in set (0.00 sec)

数据项操作

添加数据

默认情况下在命令行中 mysql 是不能直接插入中文的，这个跟字符集有关。可输入下面命令修改数据库或表的字符集:

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ALTER DATABASE danny_database character SET utf8;


ALTER TABLE customers convert to character SET utf8;

为数据表插入数据，显式设置字段

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mysql> INSERT INTO danny_database.customers(cust_id, cust_name, sex, cust_address)
    -> VALUES(901, '张三', DEFAULT, '广州市');
Query OK, 1 row affected (0.02 sec)

mysql> INSERT INTO danny_database.customers(cust_id, cust_name, sex, cust_address) 
    -> VALUES(0, '李四', DEFAULT, '广州市');
Query OK, 1 row affected (0.01 sec)

mysql> select * from customers;
+
| cust_id | cust_name | sex  | cust_city | cust_address |
+
|     901 | 张三      | M    | shenzhen  | 广州市         |
|     902 | 李四      | M    | shenzhen  | 广州市         |
+
2 rows in set (0.00 sec)

由于 cust_id 是自增的，因此可以将此字段的值设置为 0 或 NULL 会自动自增。上例 “李四” 的 cust_id 在创建后就被自增为 902。

还可以通过 SET 语句设置部分值：

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mysql> INSERT INTO danny_database.customers SET cust_name='王五', cust_address='武汉市', sex=DEFAULT;
Query OK, 1 row affected (0.00 sec)

查询数据

可通过 SELECT 语句查询数据：

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mysql> SELECT * FROM customers;
+
| cust_id | cust_name | sex  | cust_city | cust_address |
+
|     901 | 张三      | M    | shenzhen  | 广州市         |
|     902 | 李四      | M    | shenzhen  | 广州市         |
|     903 | 王五      | M    | shenzhen  | 武汉市         |
+
3 rows in set (0.00 sec)

仅展示指定字段：

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+
| cust_id | cust_name | sex  |
+
|     901 | 张三      | M    |
|     902 | 李四      | M    |
|     903 | 王五      | M    |
+
3 rows in set (0.00 sec)

通过 WHERE 子句设置查询条件，筛选出符合查询条件的数据：

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mysql> SELECT cust_id,cust_name,cust_address FROM customers
    -> WHERE cust_address="广州市";
+
| cust_id | cust_name | cust_address |
+
|     901 | 张三      | 广州市         |
|     902 | 李四      | 广州市         |
+
2 rows in set (0.00 sec)

删除数据

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mysql> INSERT INTO danny_database.customers(cust_id, cust_name, sex, cust_address) 
    -> VALUES(1, 'test1', DEFAULT, '深圳市');
Query OK, 1 row affected (0.02 sec)

mysql> select * from customers;
+
| cust_id | cust_name | sex  | cust_city | cust_address |
+
|       1 | test1    | M    | shenzhen  | 深圳市         |
|     901 | 张三      | M    | shenzhen  | 广州市         |
|     902 | 李四      | M    | shenzhen  | 广州市         |
|     903 | 王五      | M    | shenzhen  | 武汉市         |
+
4 rows in set (0.00 sec)


mysql> DELETE FROM customers
    -> WHERE cust_id=1;
Query OK, 1 row affected (0.02 sec)


mysql> select * from customers;
+
| cust_id | cust_name | sex  | cust_city | cust_address |
+
|     901 | 张三      | M    | shenzhen  | 广州市         |
|     902 | 李四      | M    | shenzhen  | 广州市         |
|     903 | 王五      | M    | shenzhen  | 武汉市         |
+

更新数据

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mysql> UPDATE customers SET cust_address="深圳市" WHERE cust_name="李四";
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM customers;
+
| cust_id | cust_name | sex  | cust_city | cust_address |
+
|     901 | 张三      | M    | shenzhen  | 广州市       |
|     902 | 李四      | M    | shenzhen  | 深圳市       |
|     903 | 王五      | M    | shenzhen  | 武汉市       |
+
3 rows in set (0.00 sec)

实践

以一个 eShop 的需求为例做个简单的测试吧。

创建 eshop 数据库

在 MySQL 中创建一个名为 eshop 的数据库，选择字符集为 utf8mb4

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mysql> CREATE DATABASE IF NOT EXISTS eshop DEFAULT CHARACTER SET utf8mb4;
Query OK, 1 row affected (0.01 sec)

mysql> SHOW DATABASES;
+
| Database           |
+
| information_schema |
| DANNY_DATABASE     |
| eshop              |
| mysql              |
| performance_schema |
| sys                |
+
6 rows in set (0.01 sec)


mysql> use eshop;
Database changed

创建数据表及相关记录

相关表信息如下

表名：用户(t_user)

字段名类型大小
用户ID (id)自增类型
姓名 (user_name)文本50，非空
联系电话 (phone_no)文本20，非空

表名：商品（product）

字段名类型大小
商品ID（id）自增类型
商品名称(product_name)文本50，非空
价格(price)数值类型（整数位9位，小数位2位），非空

表名：购物车 (shopping_cart)

字段名类型大小
用户id（user_id）整数非空，主键，参考用户表主键
商品id(product_id)整数非空，主键，参考商品表主键
商品数量(quantity)整数非空
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mysql> CREATE TABLE IF NOT EXISTS t_user(
    ->   `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->   `user_name` CHAR(50) NOT NULL,
    ->   `phone_no` CHAR(20) NOT NULL
    -> );
Query OK, 0 rows affected (0.06 sec)


mysql> CREATE TABLE IF NOT EXISTS product(
    ->   `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    ->   `product_name` CHAR(50) NOT NULL,
    ->   `price` DOUBLE(9, 2)
    -> );
Query OK, 0 rows affected (0.06 sec)


mysql> CREATE TABLE IF NOT EXISTS shopping_cart(
    ->   `user_id` INT NOT NULL,
    ->   `product_id` INT NOT NULL,
    ->   `quantity` INT NOT NULL,
    ->   PRIMARY KEY(`user_id`, `product_id`)
    -> );
Query OK, 0 rows affected (0.05 sec)


mysql> show tables;
+
| Tables_in_eshop |
+
| product         |
| shopping_cart   |
| t_user          |
+
3 rows in set (0.00 sec)

录入用户数据

用户信息

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1;张三; 13333333333;
2;李四; 13666666666
3;王五; 13888888888
4;赵六; 13999999999

商品信息

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1; C++程序设计教程; 45.5
2; 数据结构; 33.7
3; 操作系统; 51

购物车

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1; 1; 5
1; 2; 3
2; 3; 6
2; 4; 8

录入数据：

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mysql> INSERT INTO t_user
    ->   (id, user_name, phone_no)
    -> VALUES
    ->   (1, '张三', '13333333333'),
    ->   (2, '李四', '13666666666'),
    ->   (3, '王五', '13888888888'),
    ->   (4, '赵六', '13999999999');
Query OK, 4 rows affected (0.02 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM t_user;
+
| id | user_name | phone_no    |
+
|  1 | 张三      | 13333333333 |
|  2 | 李四      | 13666666666 |
|  3 | 王五      | 13888888888 |
|  4 | 赵六      | 13999999999 |
+
4 rows in set (0.00 sec)


mysql> INSERT INTO product
    ->   (id, product_name, price)
    -> VALUES
    ->   (1, 'C++程序设计教程', 45.5),
    ->   (2, '数据结构', 33.7),
    ->   (3, '操作系统', 51);
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM product;
+
| id | product_name          | price |
+
|  1 | C++程序设计教程       | 45.50 |
|  2 | 数据结构              | 33.70 |
|  3 | 操作系统              | 51.00 |
+
3 rows in set (0.00 sec)


mysql> INSERT INTO shopping_cart
    ->   (user_id, product_id, quantity)
    -> VALUES
    ->   (1, 1, 5),
    ->   (1, 2, 3),
    ->   (2, 3, 6),
    ->   (2, 4, 8);
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM shopping_cart;
+
| user_id | product_id | quantity |
+
|       1 |          1 |        5 |
|       1 |          2 |        3 |
|       2 |          3 |        6 |
|       2 |          4 |        8 |
+
4 rows in set (0.00 sec)

数据的查询与更新

使用 SQL 语句列出「张三」购买商品清单信息，以购买数量升序排列：

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mysql> SELECT u.user_name, p.product_name, u.phone_no, p.price, s.quantity FROM t_user u, product p, shopping_cart s
    -> WHERE u.user_name="张三" AND u.id = s.user_id  AND p.id = s.product_id 
    -> ORDER BY quantity asc
    -> LIMIT 100;
+
| user_name | product_name          | phone_no    | price | quantity |
+
| 张三      | 数据结构              | 13333333333 | 33.70 |        3 |
| 张三      | C++程序设计教程       | 13333333333 | 45.50 |        5 |
+
2 rows in set (0.01 sec)

使用 SQL 语句选出李四购买商品的总价：

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mysql> SELECT u.user_name, p.product_name, p.price, s.quantity, p.price*s.quantity AS total_price FROM t_user u, product p, shopping_cart s
    -> WHERE u.user_name="李四" AND u.id = s.user_id  AND p.id = s.product_id 
    -> LIMIT 100;
+
| user_name | product_name | price | quantity | total_price |
+
| 李四      | 操作系统     | 51.00 |        6 |      306.00 |
+
1 row in set (0.00 sec)

使用 SQL 语句列出购买数量排前两位的商品名称：

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mysql> SELECT p.product_name, p.price, s.quantity FROM product p, shopping_cart s
    -> WHERE p.id = s.product_id
    -> ORDER BY quantity desc
    -> LIMIT 2;
+
| product_name          | price | quantity |
+
| 操作系统              | 51.00 |        6 |
| C++程序设计教程       | 45.50 |        5 |
+
2 rows in set (0.00 sec)

忘记密码

若忘记数据库密码后可通过 mysqld_safe 来修改密码：

  1. 在系统偏好设置中关闭 mysql 服务

  2. 打开终端，输入命令:

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    ➜  ~ cd /usr/local/mysql/bin
    ➜  ~ sudo su

  3. 命令行变成以 sh-3.2# 开头后继续输入命令:

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    sh-3.2

    mysqld_safe Logging to '/usr/local/mysql/data/DannydeMBP.err'. 
    mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/data

  4. 新开个命令行窗口，进入 mysql:

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    ➜  ~ /usr/local/mysql/bin/mysql

    Enter password:
    Welcome to the MySQL monitor.  Commands end with ; or \g.
    Your MySQL connection id is 30
    Server version: 5.7.31

    Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.

    Oracle is a registered trademark of Oracle Corporation and/or its
    affiliates. Other names may be trademarks of their respective
    owners.

    Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

    mysql>
    mysql> use mysql

    Reading table information for completion of table and column names
    You can turn off this feature to get a quicker startup with -A

    Database changed

  5. 更新密码

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    mysql> update user set authentication_string=password('admin') where Host='localhost' and User='root';

    Query OK, 1 row affected, 1 warning (0.01 sec)
    Rows matched: 1  Changed: 1  Warnings: 1

  6. 输入 exit 命令退出 mysql，查出 mysqld_safe 进程号并杀掉:

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    mysql> exit
    Bye

    ➜  ~ ps -ax | grep mysql
      8553 ttys004    0:00.03 /bin/sh ./mysqld_safe --skip-grant-tables
      8623 ttys004    0:00.92 /usr/local/mysql-5.7.31-macos10.14-x86_64/bin/mysqld --basedir=/usr/local/mysql-5.7.31-macos10.14-x86_64 --datadir=/usr/local/mysql-5.7.31-macos10.14-x86_64/data --plugin-dir=/usr/local/mysql-5.7.31-macos10.14-x86_64/lib/plugin --user=mysql --skip-grant-tables --log-error=host-3-187.can.danny1.network.err --pid-file=host-3-187.can.danny1.network.pid


    ➜  ~ kill -9 8553
    ➜  ~ kill -9 8623

  7. 此时返回系统偏好设置中看到 mysql 被关闭后就算正确退出了。接着继续输入 mysql -u root -p 命令连接数据库，再输入刚才修改的密码即可。

参考资料