ALTER TABLE 資料名名稱 ADD 欄位名稱column_name datatype;
//例如新增createdAt 欄位
ALTER TABLE tests ADD createdAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP;
//例如新增discount 欄位
ALTER TABLE users ADD discount DECIMAL(10, 2);

ALTER TABLE 資料名名稱 DROP COLUMN 欄位名稱column_name;
//刪除discount 欄位
ALTER TABLE users DROP discount;

SELECT `Name` AS `C_Name`, `City` AS `C_City`,`Salary` FROM `customers`;

SELECT o.Product, SUM(o.Quantity) AS Total FROM orders AS o GROUP BY o.Product;

create 資料庫名稱;

CREATE TABLE table_name (
  column_name1 data_type,
  column_name2 data_type,
  column_name3 data_type,
  ···
);

CREATE TABLE `users` ( 
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    uId INT NOT NULL UNIQUE, 
    userName VARCHAR(30) NOT NULL, 
    userEmail VARCHAR(50) NOT NULL, 
    userPassword VARCHAR(30) NOT NULL, 
    userPhone VARCHAR(10) NOT NULL, 
    roleId INT NOT NULL, 
    createdAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    updatedAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    deletedAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP 
);
CREATE TABLE `users` (
    id INT NOT NULL AUTO_INCREMENT, 
    uId INT NOT NULL, 
    userName VARCHAR(50) NOT NULL, 
    userEmail VARCHAR(30)NOT NULL, 
    userPassword VARCHAR(30) NOT NULL, 
    userPhone VARCHAR(10) NOT NULL, 
    roleId INT NOT NULL, 
    createdAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    updatedAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    deletedAt TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP , 
    PRIMARY KEY (id), 
    UNIQUE (uId) 
);

create database demo_db;
Query OK, 1 row affected (0.00 sec)
show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| demo_db            |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

//使用資料庫
use  demo_db
//建立table 
create table person(name varchar(20),phone varchar(20),age int);
Query OK, 0 rows affected (0.04 sec)

//指令
desc person;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| name  | varchar(20) | YES  |     | NULL    |       |
| phone | varchar(20) | YES  |     | NULL    |       |
| age   | int(11)     | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.01 sec)

show tables;
+-------------------+
| Tables_in_demo_db |
+-------------------+
| person            |
+-------------------+
1 row in set (0.00 sec)

show columns from person;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| name  | varchar(20) | YES  |     | NULL    |       |
| phone | varchar(20) | YES  |     | NULL    |       |
| age   | int(11)     | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+

show tables;
+-------------------+
| Tables_in_demo_db |
+-------------------+
| person            |
| products          |
+-------------------+
2 rows in set (0.00 sec)

//刪除table
drop table products;
Query OK, 0 rows affected (0.01 sec)

show tables;
+-------------------+
| Tables_in_demo_db |
+-------------------+
| person            |
+-------------------+
1 row in set (0.00 sec)

show databases;
SHOW databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

create database test_db;
Query OK, 1 row affected (0.00 sec)

//result
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| test_db            |
+--------------------+
5 rows in set (0.00 sec)

use test_db;
Database changed

select database();
+------------+
| database() |
+------------+
| test_db    |
+------------+
1 row in set (0.00 sec)

+------------+
| database() |
+------------+
| NULL       |
+------------+
1 row in set (0.00 sec)

drop database test_db;
Query OK, 0 rows affected (0.02 sec)
//result
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

delimiter $$ 

show databases $$;

+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

delimiter ; 
當前有效
show databases $$;
show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

sudo /usr/local/mysql/support-files/mysql.server start

sudo /usr/local/mysql/support-files/mysql.server stop

sudo /usr/local/mysql/support-files/mysql.server restart

/usr/local/mysql/bin/mysql -u root -h 127.0.0.1 -p
密碼

ALTER USER 'root'@'localhost' IDENTIFIED BY '重置密碼';

cd /usr/local/mysql/support-files

sudo ./mysql.server start
Password:系統密碼
Starting MySQL
Logging to '/usr/local/mysql/data/larahuangde-MacBook-Pro.local.err'.
SUCCESS! 

cd .. 

larahuang@larahuangde-MacBook-Pro mysql % ls

LICENSE		data		keyring		share
README		docs		lib		support-files
bin		include		man

cd bin //到bin 資料夾
innochecksum			mysqlbinlog
lz4_decompress			mysqlcheck
my_print_defaults		mysqld
myisam_ftdump			mysqld-debug
myisamchk			mysqld_multi
myisamlog			mysqld_safe
myisampack			mysqldump
mysql				mysqldumpslow
mysql_client_test_embedded	mysqlimport
mysql_config			mysqlpump
mysql_config_editor		mysqlshow
mysql_embedded			mysqlslap
mysql_install_db		mysqltest_embedded
mysql_plugin			mysqlxtest
mysql_secure_installation	perror
mysql_ssl_rsa_setup		replace
mysql_tzinfo_to_sql		resolve_stack_dump
mysql_upgrade			resolveip
mysqladmin			zlib_decompress

./mysql -u root -h 127.0.0.1 -p

Enter password: 初次安裝時的密碼
//進入MySQL version: 5.7.29
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.29

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.

//一定要分號
ALTER USER 'root'@'localhost' IDENTIFIED BY '重置密碼';
Query OK, 0 rows affected (0.01 sec)
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ALTER USER 'root'@'localhost' IDENTIFIED by '新密碼''

//退出
exit 
Bye

sudo rm -rf /usr/local/var/mysql
sudo rm -rf /usr/local/mysql*
sudo rm -rf /Library/StartupItems/MySQLCOM
sudo rm -rf /Library/PreferencePanes/My*
sudo rm -rf /Library/Receipts/mysql*
sudo rm -rf /Library/Receipts/MySQL*
sudo rm -rf /private/var/db/receipts/*mysql*

<div class="container">
  <div class="content">
    <canvas  class="canvas" width="500" height="500" ></canvas>
  </div>
</div>

var canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
//檢查支援
if (canvas.getContext) {
  var ctx = canvas.getContext("2d");
  var radius = canvas.height / 2;
  console.log('radius1',radius)
  ctx.translate(radius, radius);
  radius = radius * 0.90
  console.log('radius2',radius * 0.90)
  //每一秒執行一次函式
  setInterval(drawClock, 1000);
} 


function drawClock() {
  drawFace(ctx, radius);
  drawNumbers(ctx, radius);
  drawTime(ctx, radius);
}

//塞入時鐘圖案
function drawFace(ctx, radius) {
  var grad;
  ctx.beginPath();
  ctx.arc(0, 0, radius, 0, 2*Math.PI);
  ctx.fillStyle = 'white';
  ctx.fill();
  ctx.strokeStyle = '#00bcd4'; //外框顏色
  ctx.lineWidth = radius*0.1;
  ctx.stroke();
  ctx.beginPath();
  ctx.arc(0, 0, radius*0.1, 0, 2*Math.PI);
  ctx.fillStyle = '#00bcd4';//中心點顏色
  ctx.fill();
}

//塞入1~12的字樣
function drawNumbers(ctx, radius) {
  var ang;
  var num;
  ctx.font = radius*0.15 + "px arial";
  ctx.textBaseline="middle";
  ctx.textAlign="center";
  for(num = 1; num < 13; num++){
    ang = num * Math.PI / 6;
    ctx.rotate(ang);
     ctx.fillStyle = '#3333';//小時的顏色
    ctx.translate(0, -radius*0.85);
    ctx.rotate(-ang);
    ctx.fillText(num.toString(), 0, 0);
    ctx.rotate(ang);
    ctx.translate(0, radius*0.85);
    ctx.rotate(-ang);
  }
}


function drawTime(ctx, radius){
    var now = new Date();
    var hour = now.getHours();
    var minute = now.getMinutes();
    var second = now.getSeconds();
    //hour
    hour=hour%12;
    hour=(hour*Math.PI/6)+
    (minute*Math.PI/(6*60))+
    (second*Math.PI/(360*60));
    drawHand(ctx, hour, radius*0.5, radius*0.07);
    //minute
    minute=(minute*Math.PI/30)+(second*Math.PI/(30*60));
    drawHand(ctx, minute, radius*0.8, radius*0.07);
    // second
    second=(second*Math.PI/30);
    drawHand(ctx, second, radius*0.9, radius*0.02);
}


function drawHand(ctx, pos, length, width) {
    ctx.beginPath();
    ctx.strokeStyle = '#3f51b5';//指針顏色
    ctx.lineWidth = width;
    ctx.lineCap = "round";
    ctx.moveTo(0,0);
    ctx.rotate(pos);
    ctx.lineTo(0, -length);
    ctx.stroke();
    ctx.rotate(-pos);
}