#? ?Mysql基本語(yǔ)法
###? 基礎(chǔ)命令
```
java
show databses;//查看數(shù)據(jù)庫(kù)列表
create databse shop;//創(chuàng)建一個(gè)名為shop的數(shù)據(jù)庫(kù)
use shop;//使用shop庫(kù)
creat table Product;//建一張名為Product的表
CREATE TABLE Product(id int not NULL PRIMARY KEY auto_increment);
//包含一個(gè)id字段 字段類(lèi)型為int（整數(shù)）not null表示不允許為空null，promary key 表示該字段為主鍵缸逃，auto_incremn表示該id自動(dòng)增加
desc Product; //查詢(xún)表結(jié)構(gòu)
ALTER TABLE Product add COLUMN name VARCHAR(100);//更新表結(jié)構(gòu)
ALTER TABLE Product drop COLUMN name; //刪除部分表結(jié)構(gòu)
INSERT INTO Product(name,price,type) VALUES ("帽子",99,"服飾");//添加數(shù)據(jù)
//查詢(xún)Product表中全部的數(shù)據(jù)
select*from Product;
DELETE FROM Product where id =1;//刪除表中id為1的數(shù)據(jù)
UPDATE Product set name ="拖鞋" WHERE id = 2;//修改Product 表中id為2的記錄name 值為拖鞋
SELECT*FROM Product WHERE type ="服飾" and price >=100;//查詢(xún)多個(gè)條件
SELECT*FROM Product WHERE type ="服飾";//查詢(xún)一個(gè)條件
SELECT type FROM Product;//查詢(xún)指定內(nèi)容
SELECT type FROM Product GROUP BY type;//分組查詢(xún)
SELECT DISTINCT type FROM Product type;//分組查詢(xún)時(shí)去掉重復(fù)值
? ? ? ? SELECT type,COUNT(*) FROM Product? GROUP BY type;//分組查詢(xún)并計(jì)算總數(shù)
? ? ? ? SELECT name,price FROM Product;//多字段查詢(xún)
? ? ? ? SELECT name ,price,price * 0.8 As price2 FROM Product;//對(duì)字段進(jìn)行操作并命名
SELECT name AS Product_name ,price,price * 0.8 As price2 FROM Product;//多字段操作并命名
? ? ? ? SELECT name ,price,price * 0.8 AS price2 FROM Product WHERE price>150;//條件篩選操作并命名
? ? ? ? SELECT name ,price,price * 0.9 AS price2 FROM Product WHERE price<150 and type ='衣服';//多條件篩選并命名
select sum(price) from Product;//計(jì)算總和
select avg(price) from Product;//計(jì)算平均價(jià)格
select min(price) from Product;//計(jì)算最小值
select max(price) from Product;//計(jì)算最大值
```
