Navicat使用
下载地址:<https://pan.baidu.com/s/1bpo5mqj>
Navicat是基于mysql操作的，所以能否自主完成一些练习，就能够运用Navicat
练习时需要用到的数据：
Navicat Premium Data Transfer Source Server : localhost Source Server Type : MySQL Source Server Version : 50624 Source Host : localhost Source Database : sqlexam Target Server Type : MySQL Target Server Version : 50624 File Encoding : utf-8 Date: 10/21/2016 06:46:46 AM */ SET NAMES utf8; SET FOREIGN_KEY_CHECKS = 0; -- ---------------------------- -- Table structure for `class` -- ---------------------------- DROP TABLE IF EXISTS `class`; CREATE TABLE `class` ( `cid` int(11) NOT NULL AUTO_INCREMENT, `caption` varchar(32) NOT NULL, PRIMARY KEY (`cid`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `class` -- ---------------------------- BEGIN; INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班'); COMMIT; -- ---------------------------- -- Table structure for `course` -- ---------------------------- DROP TABLE IF EXISTS `course`; CREATE TABLE `course` ( `cid` int(11) NOT NULL AUTO_INCREMENT, `cname` varchar(32) NOT NULL, `teacher_id` int(11) NOT NULL, PRIMARY KEY (`cid`), KEY `fk_course_teacher` (`teacher_id`), CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `course` -- ---------------------------- BEGIN; INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2'); COMMIT; -- ---------------------------- -- Table structure for `score` -- ---------------------------- DROP TABLE IF EXISTS `score`; CREATE TABLE `score` ( `sid` int(11) NOT NULL AUTO_INCREMENT, `student_id` int(11) NOT NULL, `course_id` int(11) NOT NULL, `num` int(11) NOT NULL, PRIMARY KEY (`sid`), KEY `fk_score_student` (`student_id`), KEY `fk_score_course` (`course_id`), CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`), CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`) ) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `score` -- ---------------------------- BEGIN; INSERT INTO `score` VALUES ('1', '1', '1', '10'), ('2', '1', '2', '9'), ('5', '1', '4', '66'), ('6', '2', '1', '8'), ('8', '2', '3', '68'), ('9', '2', '4', '99'), ('10', '3', '1', '77'), ('11', '3', '2', '66'), ('12', '3', '3', '87'), ('13', '3', '4', '99'), ('14', '4', '1', '79'), ('15', '4', '2', '11'), ('16', '4', '3', '67'), ('17', '4', '4', '100'), ('18', '5', '1', '79'), ('19', '5', '2', '11'), ('20', '5', '3', '67'), ('21', '5', '4', '100'), ('22', '6', '1', '9'), ('23', '6', '2', '100'), ('24', '6', '3', '67'), ('25', '6', '4', '100'), ('26', '7', '1', '9'), ('27', '7', '2', '100'), ('28', '7', '3', '67'), ('29', '7', '4', '88'), ('30', '8', '1', '9'), ('31', '8', '2', '100'), ('32', '8', '3', '67'), ('33', '8', '4', '88'), ('34', '9', '1', '91'), ('35', '9', '2', '88'), ('36', '9', '3', '67'), ('37', '9', '4', '22'), ('38', '10', '1', '90'), ('39', '10', '2', '77'), ('40', '10', '3', '43'), ('41', '10', '4', '87'), ('42', '11', '1', '90'), ('43', '11', '2', '77'), ('44', '11', '3', '43'), ('45', '11', '4', '87'), ('46', '12', '1', '90'), ('47', '12', '2', '77'), ('48', '12', '3', '43'), ('49', '12', '4', '87'), ('52', '13', '3', '87'); COMMIT; -- ---------------------------- -- Table structure for `student` -- ---------------------------- DROP TABLE IF EXISTS `student`; CREATE TABLE `student` ( `sid` int(11) NOT NULL AUTO_INCREMENT, `gender` char(1) NOT NULL, `class_id` int(11) NOT NULL, `sname` varchar(32) NOT NULL, PRIMARY KEY (`sid`), KEY `fk_class` (`class_id`), CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`) ) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `student` -- ---------------------------- BEGIN; INSERT INTO `student` VALUES ('1', '男', '1', '理解'), ('2', '女', '1', '钢蛋'), ('3', '男', '1', '张三'), ('4', '男', '1', '张一'), ('5', '女', '1', '张二'), ('6', '男', '1', '张四'), ('7', '女', '2', '铁锤'), ('8', '男', '2', '李三'), ('9', '男', '2', '李一'), ('10', '女', '2', '李二'), ('11', '男', '2', '李四'), ('12', '女', '3', '如花'), ('13', '男', '3', '刘三'), ('14', '男', '3', '刘一'), ('15', '女', '3', '刘二'), ('16', '男', '3', '刘四'); COMMIT; -- ---------------------------- -- Table structure for `teacher` -- ---------------------------- DROP TABLE IF EXISTS `teacher`; CREATE TABLE `teacher` ( `tid` int(11) NOT NULL AUTO_INCREMENT, `tname` varchar(32) NOT NULL, PRIMARY KEY (`tid`) ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `teacher` -- ---------------------------- BEGIN; INSERT INTO `teacher` VALUES ('1', '张磊老师'), ('2', '李平老师'), ('3', '刘海燕老师'), ('4', '朱云海老师'), ('5', '李杰老师'); COMMIT; SET FOREIGN_KEY_CHECKS = 1;
拷贝上述代码，新建一个.sql文件，保存到桌面
打开navicat新建数据库day41，选中新建的数据库鼠标右键选择运行SQL文件
弹出文件框，选中刚刚保存到桌面的.sql文件即可
练习题：
1、查询所有的课程的名称以及对应的任课老师姓名 2、查询平均成绩大于八十分的同学的姓名和平均成绩 3、查询没有报李平老师课的学生姓名 4、 查询没有同时选修物理课程和体育课程的学生姓名 5、 查询挂科超过两门(包括两门)的学生姓名和班级
参考答案
1、查询所有的课程的名称以及对应的任课老师姓名 SELECT course.cname, teacher.tname FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid; 2、查询平均成绩大于八十分的同学的姓名和平均成绩 SELECT student.sname, t1.avg_num FROM student INNER JOIN ( SELECT student_id, avg(num) AS avg_num FROM score GROUP BY student_id HAVING avg(num) > 80 ) AS t1 ON student.sid = t1.student_id; 3、查询没有报李平老师课的学生姓名(找出报名李平老师课程的学生，然后取反就可以) SELECT student.sname FROM student WHERE sid NOT IN ( SELECT DISTINCT student_id FROM score WHERE course_id IN ( SELECT course.cid FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid WHERE teacher.tname = '李平老师' ) ); 4、询没有同时选修物理课程和体育课程的学生姓名(没有同时选修指的是选修了一门的，思路是得到物理+体育课程的学生信息表，然后基于学生分组，统计count(课程)=1) SELECT student.sname FROM student WHERE sid IN ( SELECT student_id FROM score WHERE course_id IN ( SELECT cid FROM course WHERE cname = '物理' OR cname = '体育' ) GROUP BY student_id HAVING COUNT(course_id) = 1 ); 5、查询挂科超过两门(包括两门)的学生姓名和班级 select student.sname,class.caption from class INNER JOIN student on class.cid = student.class_id WHERE student.sid in (select student_id from score where num < 60 GROUP BY student_id HAVING COUNT(course_id) >=2) ;
用Python操作数据库
python
1.安装:pip3 insatll pymysql
2.代码链接
import pymysql
链接
conn=pymysql.connect(
host='localhost',
user='root',
password='123',
database='egon',
charset='utf8')
游标
cursor=conn.cursor() #执行完毕返回的结果集默认以元组显示
cursor=conn.cursor(cursor=pymysql.cursors.DictCursor) # 以字典的方式显示数据
3.pymysql操作数据库
执行sql语句
user = input(">>>:").strip()
pwd = input(">>>:").strip()
sql='select * from userinfo where name="%s" and password="%s"' %(user,pwd) #注意%s需要加引号
rows=cursor.execute(sql) #执行sql语句，返回sql查询成功的记录数目
获取真实数据cursor.fetchone(),cursor.fetchall(),cursor.fetchmany(),类似管道取值，获取一条，所有，多条
cursor.scroll(1,'relative') # 相对移动
cursor.scroll(3,'absolute') # 绝对移动
cursor.close()
conn.close()
完整的操作示例：
import pymysql conn = pymysql.connect( host = '127.0.0.1', port = 3306, user = 'root', password = '123', database = 'day41', charset = 'utf8' ) cursor = conn.cursor(pymysql.cursors.DictCursor) # 将查询结果做成字典的格式 res = cursor.execute("select * from class") print(res) # 查询到的数据总条数 print(cursor.fetchone()) # 获取一条查询结果 # print(cursor.fetchone()) # 获取一条查询结果 # print(cursor.fetchone()) # 获取一条查询结果 # cursor.scroll(1,'absolute') # 绝对移动，参照开始位置 cursor.scroll(1,'relative') print(cursor.fetchone()) # print(cursor.fetchall()) # 获取所有查询到的数据
sql注入问题
import pymysql conn = pymysql.connect( host = '127.0.0.1', port = 3306, user = 'root', password = '123', database = 'day41', charset = 'utf8', autocommit = True ) cursor = conn.cursor(pymysql.cursors.DictCursor) username = input('username>>>:') password = input('password>>>:') sql = "insert into userinfo(name,password) values(%s,%s)" # sql = "update userinfo set name='jasonhs' where id =1" # sql = "select * from userinfo where name=%s and password=%s" res = cursor.execute(sql,(username,password)) # res = cursor.execute(sql) # conn.commit() # 确认数据无误之后 commit之后才会将数据真正修改到数据库 print(sql) if res: # print(cursor.fetchall()) pass else: print('用户名或密码错误！')
不要手动去拼接查询的sql语句
username = input(">>>:").strip()
password = input(">>>:").strip()
sql = "select * from user where username='%s' and password='%s'"%(username,password)
用户名正确
username >>>: jason' -- jjsakfjjdkjjkjs
用户名密码都不对的情况
username >>>: xxx' or 1=1 --asdjkdklqwjdjkjasdljad
password >>>: ''
增删改
# 增
sql = "insert into user(username,password) values(%s,%s)"
rows = cursor.excute(sql,('jason','123'))
# 修改
sql = "update user set username='jasonDSB' where id=1"
rows = cursor.excute(sql)
增和改单单执行excute并不会真正影响到数据，需要再执行conn.commit()才可以完成真正的增改
# 一次插入多行记录
res = cursor,excutemany(sql,[(),(),()]