链接本地数据库，下载xampp以及Navicat
查询表中某个字段
SELECT name FROM ylan_student
查询表中多个字段
SELECT name,age FROM ylan_student
关键词 DISTINCT 用于返回唯一不同的值
SELECT DISTINCT age FROM ylan_student
选取年龄大于23的人的姓名
SELECT name FROM ylan_student WHERE age > 23
年龄为23且为女性的人的信息
SELECT * FROM ylan_student WHERE age=23 AND sex='女'
SELECT * FROM ylan_student WHERE age=23 OR sex='女'
SELECT * FROM ylan_student WHERE(age=23 OR age=21)AND sex='男'
年龄排序
SELECT * FROM ylan_student ORDER BY age
插入一条数据(全部字段)
INSERT INTO ylan_student VALUES('李喜光',24,'男',1,1)
更新数据
UPDATE ylan_student SET name = 'arc' WHERE name = '李喜光'AND age=24
删除数据
DELETE FROM ylan_student WHERE name = 'adc'
删除所有行
DELETE FROM ylan_student
创建表
CREATE TABLE Persons
(
//自动增加
Id_P int NOT NULL AUTO_INCREMENT,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255),
//主键
PRIMARY KEY(id_P)
)
修改表名
rename table Persons to ylan_student2
取三条数据
SELECT *
FROM ylan_student
LIMIT 3
COUNT(*) 函数返回表中的记录数：
SELECT COUNT(*)FROM table_name;
平均成绩降序排列以及学生的信息
SELECT (score.mathe + score.chainese + score.english)/3 as avgs,student.*
FROM student,score
WHERE student.id=score.student_id ORDER BY avgs DESC;
