Mysql第二章（DML和DQL）_year(now())-year(borndate) as age

本章目标

1、掌握使用sql语句修改、删除表

2、掌握添加/删除约束的sql语句

3、掌握简单子查询的用法

4、掌握IN子查询的用法

存储引擎的类型

MyISAM、InnoDB、Memory、CSV等九种

设置表的存储引擎

create table myschool(

    dis int(3)

)engine=存储引擎    #myisam/innodb

插入单条数据

insert into 表名(字段名) values（值列表）

将查询结果插入新表

create table 表名(

    select 列名 

    from 表名

    where 条件 

    order by 列名     #desc 

)    

数据更新

update 表明 set 列名=（）

where 

删除数据记录

1,delect from 表名

where

DELETE FROM dropstudent
WHERE studentName='郭靖'

2,truncate table 表名

常用函数 聚合函数

AVG()          平均

COUNT()     行数

MAX()         最大

MIN()          最小

SUM()         求和

RAND()       返回0-1直接的某个数

练习：把成绩都降低10%后加5分，再查询及格成绩，并从高到低排序

Mysql查询语句中使用LIMIT字句限制结果集

select 字段名/列

from 表名

where 条件

group by 分组字段名

order by  排序字段名  #desc

limit (位置偏移量,行数)

SELECT `studentNo`,`studentName`,`phone`,`address`,`bornDate`
FROM student
WHERE gradeID=1
ORDER BY studentNo
LIMIT 2,3 #从第几条开始,显示几条  不写默认0 [位置偏移量，行数]

UPDATE student SET loginPwd='000',email='stu20000@163.com'
WHERE studentNo=20000
 
UPDATE `subject` SET classHour=classHour-10
WHERE classHour>200 AND gradeID=1
 
CREATE TABLE student_grade1(
	SELECT `studentName`,`sex`,`bornDate`,`phone`
	FROM student
	WHERE gradeID=1
)

1、

SELECT studentNo,studentResult
FROM result 
WHERE examDate='2016-02-17'
ORDER BY studentResult DESC
LIMIT 5

2、

SELECT studentName,YEAR(NOW())-YEAR(bornDate) AS 年龄,bornDate,phone
FROM student
WHERE sex='女'
ORDER BY 年龄 DESC
LIMIT 1,6

3、

SELECT YEAR(bornDate) AS 年份,COUNT(studentName) AS 人数
FROM student
GROUP BY 年份
HAVING 人数>2

4、

SELECT studentNo,MAX(studentResult)AS 最高分,MIN(studentResult) AS 最低分,
AVG(studentResult) AS 平均分
FROM result
WHERE examDate='2016-02-17'

SELECT `studentNo`,`loginPwd`,`studentName`,
`sex`,`gradeID`,`phone`,`address`,`bornDate`,
`email`,`identityCard`
FROM student
WHERE bornDate>
(SELECT bornDate
FROM student
WHERE studentName='李斯文')

SELECT MAX(studentResult) AS 最高分, MIN(studentResult) AS 最低分
FROM result 
WHERE subjectNo=(SELECT subjectNo FROM `subject`WHERE subjectName='Logic Java')
AND examDate=(SELECT MAX(examDate)
FROM result
WHERE subjectNo=(SELECT subjectNo FROM `subject`WHERE subjectName='Logic Java'))

SELECT studentName
FROM student
WHERE studentNo IN(SELECT studentNo #因为返回结果不是一个 要用in子查询
FROM result
WHERE subjectNo =(SELECT subjectNo FROM `subject`WHERE subjectName='Logic Java'))

SELECT studentNo,studentName
FROM student 
WHERE studentNo IN(
	SELECT studentNo
	FROM result
	WHERE examDate IN(
		SELECT MAX(examDate) 
		FROM result 
		WHERE subjectNo=(
			SELECT subjectNo 
			FROM `subject` 
			WHERE subjectName='Logic Java'))
		AND subjectNo=(
			SELECT subjectNo
			FROM `subject`
			 WHERE subjectName='Logic Java'))

NOT IN