hello mysql-CFANZ编程社区

查看当前在那哪个数据库中

select database()

修改 Student 表 AGE属性为 INT类型可以是NULL

ALTER TABLE Student MODIFY COLUMN AGE INT NULL

添加一个新列（新字段）

ALTER TABLE Student ADD NEWCOLUMN CHAR(10) NULL

删除一列（一个字段）

ALTER TABLE Student DROP NEWCOLUMN

创建表

CREATE TABLE Teacher (
  ID CHAR(16) NOT NULL
)

删除表

DROP TABLE Teacher

添加一行数据

INSERT INTO Student (ID,NAME,DESCRIPT)
VALUES("1","hongbin2","This is a descriptive")

一次添加多行数据

INSERT INTO Student VALUES("6","6号",'男',22,'a'),("7","7号",'女','18','b')
#Or
INSERT INTO Student (ID,NAME) 
VALUES("8","8号"),("9","9号")

删除数据(未必是一行)

DELETE FROM Student WHERE ID = '1'

已有的某字段改为主键
改id为主键

ALTER TABLE Student
ADD CONSTRAINT ID PRIMARY KEY(ID)

查询ID是偶数的记录全部信息

SELECT * FROM Student 
WHERE ID % 2 = 0

设置字段自动填充当前时间

ALTER TABLE store 
MODIFY COLUMN CREATEAT DATETIME NOT NULL DEFAULT NOW()
创建的时候可以不传CREATEAT字段`DEFAULT NOW()`来处理
INSERT INTO store (id,NAME,OWNER)
VALUES('2','哇哈哈','2333')

创建product表

CREATE TABLE product (
  ID CHAR(16) NOT NULL PRIMARY KEY,
  NAME CHAR(10) NOT NULL,
  OWNER CHAR(16) NOT NULL,
  CREATEAT DATETIME NOT NULL DEFAULT NOW(),
  DESCRIPT CHAR(30) NULL,
  PRICE FLOAT DEFAULT 0.0,
  QUANTITY INT NOT NULL DEFAULT 0,
  ISTRACKQUANTITY BOOLEAN DEFAULT FALSE
)

给product添加数据

INSERT INTO product(ID,NAME,PRICE,OWNER,DESCRIPT,QUANTITY) 
VALUES('p1','鸡腿',9.9,'111','OK 鸡腿',20)
VALUES('p3','乐视薯片',5,'3452','黄瓜味',50),('p4','乡巴佬鸡爪',2.0,'12345','老味道，新价钱',30)

别名
查询product表中的name字段

SELECT NAME FROM product
#Or
SELECT p.NAME FROM product  p

链接store和product表

SELECT * FROM store s INNER JOIN product p
ON p.OWNER  = s.OWNER

SELECT * FROM store s JOIN product p
WHERE p.OWNER  = s.OWNER

将store表中id改为ID
RENAME

ALTER TABLE store 
RENAME COLUMN id TO ID

更新数据将product表中storeID的值统一改成store表中对应的ID

SELECT * FROM product p 
WHERE STOREID = (SELECT OWNER FROM store WHERE OWNER = p.STOREID)

(SELECT OWNER FROM store WHERE OWNER = p.STOREID) 返回 OWNER
OWNER = STOREID 条件判断

UPDATE product p
SET STOREID = (SELECT ID FROM store WHERE OWNER = p.STOREID)

关闭 ONLY_FULL_GROUP_BY 模式

#select @@sql_mode
set @@sql_mode ='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'

查看store表中商店在product中产品的数量

SELECT s.ID,s.NAME,COUNT(*) AS 产品数量
FROM store s JOIN product p 
WHERE p.STOREID = s.ID 
GROUP BY p.STOREID

hello mysql_sql