技術標籤：MySQL資料庫mysqlsql

文章目錄

• create 語句
• • 建立資料庫
  • 使用資料庫
  • 建立資料表
• insert 語句
• • 新增資料
• delete 語句
• • 刪除資料
• update 語句
• • 更改資料
• select 語句
• • 查詢資料總數量
  • 查詢表中所有資料
  • 查詢某個欄位資料
  • 條件查詢
  • 分頁查詢
  • 模糊查詢
  • 聯表查詢
  • 最大值查詢
  • 最小值查詢
  • 平均值查詢
  • 求和查詢

create 語句

建立資料庫

create database school;

使用資料庫

use school;

建立資料表

create table student(
student_id int primary key auto_increment
 
,
student_name varchar(30),
student_score int);

create table book(
book_id int primary key auto_increment,
book_name varchar(30),
book_amount int,
student_id int,
foreign key (student_id) references student (student_id) on delete cascade);

• primary key 代表該欄位為主鍵。
• auto_increment 代表主鍵自增。
• foreign key (student_id) references student (student_id) 為外來鍵約束語句。
• on delete cascade 設定級聯刪除。

insert 語句

新增資料

insert into student (student_id, student_name, student_score) values (1, "孫悟空", 80);
insert into student (student_id, student_name, student_score) values (2, "豬八戒", 70);

insert into book (book_id, book_name, book_amount, student_id) values
 
 (1, "JAVA", 100, 1);
insert into book (book_id, book_name, book_amount, student_id) values (2, "MySQL", 90, 1);
insert into book (book_id, book_name, book_amount, student_id) values (3, "C", 80, 2);
insert into book (book_id, book_name, book_amount, student_id) values (4, "C++", 70, 2);

delete 語句

刪除資料

delete from book where book_id = 1;

delete from student where student_id = 2;

update 語句

執行 insert 語句，使之恢復原來狀態。

更改資料

update book set book_amount = 200 where book_id = 1; 

update book set book_amount = 500 where student_id = 2; 

select 語句

查詢資料總數量

 select count(1) from book;

查詢表中所有資料

select * from book;

查詢某個欄位資料

select book_name from book;

條件查詢

select * from book where book_id = 1;

分頁查詢

select * from book limit 1,3;

模糊查詢

select * from book where book_name like "%C%";

聯表查詢

select * from student, book where book.book_id = student.student_id;

最大值查詢

select max(book_amount) from book;

最小值查詢

select min(book_amount) from book;

平均值查詢

select avg(book_amount) from book;

求和查詢

select sum(book_amount) from book;