1 練習題和sql語句
  2 
  3 基礎sql語句
  4 
  5 統計每個學生的總分。
  6 統計出學號和總分
  7    select s_id , sum(s_score) as zf  from  score  group  by s_id
  8  
  9 上表結果和stuent做join連線
 10 
 11 select stu.s_name,zf.ss from
 12  
 13 (select s_id , sum(s_score) as ss from score group by s_id) as  zf
 14  
 15 Join
 16  
 17
 
 student  as stu
 18  
 19 on  stu.s_id=zf.s_id;
 20 2.查詢表中所有學生的姓名和對應的英語成績。
 21 
 22 select stu.s_name,c.c_name,s.s_score from
 23  
 24      score as s 
 25  
 26      join
 27  
 28      course as c
 29  
 30      on s.c_id=c.c_id
 31  
 32      join
 33  
 34      student as stu
 35  
 36      on stu.s_id =
 
 s.s_id
 37  
 38      where
 39  
 40      c.c_name = 'english';
 41 3. 在所有學生總分數上加10分特長分。
 42 
 43 關鍵程式碼
 44 
 45   select s_id,sum(s_score)+10 from score group by s_id;
 46  
 47 查詢姓名為liyun的學生總成績
 48  select sum(s_score) from score where  s_id in (select s_id from student where        s_name='liyun');
 
 49  
 50 查詢英語成績大於90分的同學
 51 
 52  
 53 
 54 8.查詢總分大於270分的所有同學
 55 
 56  
 57 
 58 查詢英語分數在 80－90之間的同學。
 59  
 60 
 61 查詢數學分數為89,90,91的同學。
 62  
 63 
 64 查詢所有姓li的學生平均成績。
 65  
 66 
 67 查詢數學分>80，語文分>80的同學。
 68  
 69 
 70 對數學成績排序後輸出。
 71  
 72 
 73 對總分排序後輸出，然後再按從高到低的順序輸出
 74  
 75 
 76  對姓li的學生數學成績排序輸出
 77  
 78 
 79  
 80 
 81 有一定難度的sql語句
 82 
 83 
 84  
 85 -- 1、查詢"01"課程比"02"課程成績高的學生的資訊及課程分數  
 86 思路：
 87 關鍵步驟：
 88 select * from score l join score r on (l.s_id = r.s_id and l.c_id=2 and r.c_id=1); 
 89  
 90 select a.* ,b.s_score as 01_score,c.s_score as 02_score from 
 91     student a 
 92     join score b on a.s_id=b.s_id and b.c_id='01'
 93     left join score c on a.s_id=c.s_id and c.c_id='02' or c.c_id = NULL where b.s_score>c.s_score
 94 -- 2、查詢"01"課程比"02"課程成績低的學生的資訊及課程分數
 95 select a.* ,b.s_score as 01_score,c.s_score as 02_score from 
 96     student a left join score b on a.s_id=b.s_id and b.c_id='01' or b.c_id=NULL 
 97      join score c on a.s_id=c.s_id and c.c_id='02' where b.s_score<c.s_score
 98 -- 3、查詢平均成績大於等於60分的同學的學生編號和學生姓名和平均成績
 99 select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from 
100     student b 
101     join score a on b.s_id = a.s_id
102     GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)>=60;
103 -- 4、查詢平均成績小於60分的同學的學生編號和學生姓名和平均成績
104 -- (包括有成績的和無成績的)
105 select b.s_id,b.s_name,ROUND(AVG(a.s_score),2) as avg_score from 
106     student b 
107     left join score a on b.s_id = a.s_id
108     GROUP BY b.s_id,b.s_name HAVING ROUND(AVG(a.s_score),2)<60
109     unionselect a.s_id,a.s_name,0 as avg_score from 
110     student a 
111     where a.s_id not in (
112                 select distinct s_id from score);
113 -- 5、查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績
114 select a.s_id,a.s_name,count(b.c_id) as sum_course,sum(b.s_score) as sum_score from 
115     student a 
116     left join score b on a.s_id=b.s_id
117     GROUP BY a.s_id,a.s_name;
118 -- 6、查詢"李"姓老師的數量 
119 select a.* from 
120     student a 
121     join score b on a.s_id=b.s_id where b.c_id in(
122         select c_id from course where t_id =(
123             select t_id from teacher where t_name = '張三'));
124 -- 7、查詢學過"張三"老師授課的同學的資訊 
125 select a.* from 
126     student a 
127     join score b on a.s_id=b.s_id where b.c_id in(
128         select c_id from course where t_id =(
129             select t_id from teacher where t_name = '張三'));
130 -- 8、查詢沒學過"張三"老師授課的同學的資訊 
131  select * from student c 
132     where c.s_id not in(
133         select a.s_id from student a join score b on a.s_id=b.s_id where b.c_id in(
134             select c_id from course where t_id =(
135                 select t_id from teacher where t_name = '張三')));-- 9、查詢學過編號為"01"並且也學過編號為"02"的課程的同學的資訊
136 select a.* from 
137     student a,score b,score c 
138     where a.s_id = b.s_id  and a.s_id = c.s_id and b.c_id='01' and c.c_id='02';
139 -- 10、查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的資訊
140 select a.* from 
141     student a 
142     where a.s_id in (select s_id from score where c_id='01' ) and a.s_id not in(select s_id from score where c_id='02')
143 -- 11、查詢沒有學全所有課程的同學的資訊 
144 select s.* from 
145     student s where s.s_id in(
146         select s_id from score where s_id not in(
147             select a.s_id from score a 
148                 join score b on a.s_id = b.s_id and b.c_id='02'
149                 join score c on a.s_id = c.s_id and c.c_id='03'
150             where a.c_id='01'))
151 -- 12、查詢至少有一門課與學號為"01"的同學所學相同的同學的資訊 
152 select * from student where s_id in(
153     select distinct a.s_id from score a where a.c_id in(select a.c_id from score a where a.s_id='01')
154     );
155 -- 13、查詢和"01"號的同學學習的課程完全相同的其他同學的資訊 
156 select a.* from student a where a.s_id in(
157     select distinct s_id from score where s_id!='01' and c_id in(select c_id from score where s_id='01')
158     group by s_id 
159     having count(1)=(select count(1) from score where s_id='01'));-- 14、查詢沒學過"張三"老師講授的任一門課程的學生姓名 select a.s_name from student a where a.s_id not in (
160     select s_id from score where c_id = 
161                 (select c_id from course where t_id =(
162                     select t_id from teacher where t_name = '張三')) 
163                 group by s_id);
164 -- 15、查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績
165  select a.s_id,a.s_name,ROUND(AVG(b.s_score)) from 
166     student a 
167     left join score b on a.s_id = b.s_id
168     where a.s_id in(
169             select s_id from score where s_score<60 GROUP BY  s_id having count(1)>=2)
170     GROUP BY a.s_id,a.s_name
171 -- 16、檢索"01"課程分數小於60，按分數降序排列的學生資訊select a.*,b.c_id,b.s_score from 
172  student a,score b 
173     where a.s_id = b.s_id and b.c_id='01' and b.s_score<60 ORDER BY b.s_score DESC;
174 -- 17、按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績
175 select a.s_id,(select s_score from score where s_id=a.s_id and c_id='01') as 語文,
176                 (select s_score from score where s_id=a.s_id and c_id='02') as 數學,
177                 (select s_score from score where s_id=a.s_id and c_id='03') as 英語,
178             round(avg(s_score),2) as 平均分 from score a  GROUP BY a.s_id ORDER BY 平均分 DESC;
179 -- 18.查詢各科成績最高分、最低分和平均分：以如下形式顯示：課程ID，課程name，最高分，最低分，平均分，及格率，中等率，優良率，優秀率--及格為>=60，中等為：70-80，優良為：80-90，優秀為：>=90select 
180 a.c_id,b.c_name,MAX(s_score),MIN(s_score),ROUND(AVG(s_score),2),
181     ROUND(100*(SUM(case when a.s_score>=60 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 及格率,
182     ROUND(100*(SUM(case when a.s_score>=70 and a.s_score<=80 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 中等率,
183     ROUND(100*(SUM(case when a.s_score>=80 and a.s_score<=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 優良率,
184     ROUND(100*(SUM(case when a.s_score>=90 then 1 else 0 end)/SUM(case when a.s_score then 1 else 0 end)),2) as 優秀率
185     from score a left join course b on a.c_id = b.c_id GROUP BY a.c_id,b.c_name
186 -- 19、按各科成績進行排序，並顯示排名(實現不完全)
187 -- mysql沒有rank函式
188     select a.s_id,a.c_id,
189         @i:=@i +1 as i保留排名,
190         @k:=(case when @score=a.s_score then @k else @i end) as rank不保留排名,
191         @score:=a.s_score as score
192     from (
193         select s_id,c_id,s_score from score WHERE c_id='01' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
194 )a,(select @k:=0,@i:=0,@score:=0)s
195     union
196     select a.s_id,a.c_id,
197         @i:=@i +1 as i,
198         @k:=(case when @score=a.s_score then @k else @i end) as rank,
199         @score:=a.s_score as score
200     from (
201         select s_id,c_id,s_score from score WHERE c_id='02' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
202 )a,(select @k:=0,@i:=0,@score:=0)s
203     union
204     select a.s_id,a.c_id,
205         @i:=@i +1 as i,
206         @k:=(case when @score=a.s_score then @k else @i end) as rank,
207         @score:=a.s_score as score
208     from (
209         select s_id,c_id,s_score from score WHERE c_id='03' GROUP BY s_id,c_id,s_score ORDER BY s_score DESC
210 )a,(select @k:=0,@i:=0,@score:=0)s
211 -- 20、查詢學生的總成績並進行排名select a.s_id,
212  @i:=@i+1 as i,
213     @k:=(case when @score=a.sum_score then @k else @i end) as rank,
214     @score:=a.sum_score as scorefrom (select s_id,SUM(s_score) as sum_score from score GROUP BY s_id ORDER BY sum_score DESC)a,
215     (select @k:=0,@i:=0,@score:=0)s
216 -- 21、查詢不同老師所教不同課程平均分從高到低顯示 
217  select a.t_id,c.t_name,a.c_id,ROUND(avg(s_score),2) as avg_score from course a
218         left join score b on a.c_id=b.c_id 
219         left join teacher c on a.t_id=c.t_id
220         GROUP BY a.c_id,a.t_id,c.t_name ORDER BY avg_score DESC;-- 22、查詢所有課程的成績第2名到第3名的學生資訊及該課程成績
221  
222             
223 select d.*,c.排名,c.s_score,c.c_id from (
224                 select a.s_id,a.s_score,a.c_id,@i:=@i+1 as 排名 from score a,(select @i:=0)s where a.c_id='01'    
225             )c
226             left join student d on c.s_id=d.s_id
227             where 排名 BETWEEN 2 AND 3
228             UNION
229             select d.*,c.排名,c.s_score,c.c_id from (
230                 select a.s_id,a.s_score,a.c_id,@j:=@j+1 as 排名 from score a,(select @j:=0)s where a.c_id='02'    
231             )c
232             left join student d on c.s_id=d.s_id
233             where 排名 BETWEEN 2 AND 3
234             UNION
235             select d.*,c.排名,c.s_score,c.c_id from (
236                 select a.s_id,a.s_score,a.c_id,@k:=@k+1 as 排名 from score a,(select @k:=0)s where a.c_id='03'    
237             )c
238             left join student d on c.s_id=d.s_id
239             where 排名 BETWEEN 2 AND 3;
240 -- 23、統計各科成績各分數段人數：課程編號,課程名稱,[100-85],[85-70],[70-60],[0-60]及所佔百分比
241 select distinct f.c_name,a.c_id,b.`85-100`,b.百分比,c.`70-85`,c.百分比,d.`60-70`,d.百分比,e.`0-60`,e.百分比 from score a
242                 left join (select c_id,SUM(case when s_score >85 and s_score <=100 then 1 else 0 end) as `85-100`,
243                                             ROUND(100*(SUM(case when s_score >85 and s_score <=100 then 1 else 0 end)/count(*)),2) as 百分比
244                                 from score GROUP BY c_id)b on a.c_id=b.c_id
245                 left join (select c_id,SUM(case when s_score >70 and s_score <=85 then 1 else 0 end) as `70-85`,
246                                             ROUND(100*(SUM(case when s_score >70 and s_score <=85 then 1 else 0 end)/count(*)),2) as 百分比
247                                 from score GROUP BY c_id)c on a.c_id=c.c_id
248                 left join (select c_id,SUM(case when s_score >60 and s_score <=70 then 1 else 0 end) as `60-70`,
249                                             ROUND(100*(SUM(case when s_score >60 and s_score <=70 then 1 else 0 end)/count(*)),2) as 百分比
250                                 from score GROUP BY c_id)d on a.c_id=d.c_id
251                 left join (select c_id,SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end) as `0-60`,
252                                             ROUND(100*(SUM(case when s_score >=0 and s_score <=60 then 1 else 0 end)/count(*)),2) as 百分比
253                                 from score GROUP BY c_id)e on a.c_id=e.c_id
254                 left join course f on a.c_id = f.c_id
255 -- 24、查詢學生平均成績及其名次 
256   select a.s_id,
257                 @i:=@i+1 as '不保留空缺排名',
258                 @k:=(case when @avg_score=a.avg_s then @k else @i end) as '保留空缺排名',
259                 @avg_score:=avg_s as '平均分'
260         from (select s_id,ROUND(AVG(s_score),2) as avg_s from score GROUP BY s_id)a,(select @avg_score:=0,@i:=0,@k:=0)b;
261 
262 -- 25、查詢各科成績前三名的記錄    
263 -- 1.選出b表比a表成績大的所有組       
264 -- 2.選出比當前id成績大的 小於三個的
265 select a.s_id,a.c_id,a.s_score from score a 
266             left join score b on a.c_id = b.c_id and a.s_score<b.s_score
267             group by a.s_id,a.c_id,a.s_score HAVING COUNT(b.s_id)<3
268             ORDER BY a.c_id,a.s_score DESC
269 -- 26、查詢每門課程被選修的學生數
270  select c_id,count(s_id) from score a GROUP BY c_id
271 -- 27、查詢出只有兩門課程的全部學生的學號和姓名 
272   select s_id,s_name from student where s_id in(
273                 select s_id from score GROUP BY s_id HAVING COUNT(c_id)=2);
274 -- 28、查詢男生、女生人數 
275 select s_sex,COUNT(s_sex) as 人數  from student GROUP BY s_sex
276 -- 29、查詢名字中含有"風"字的學生資訊
277  select * from student where s_name like '%風%';
278 -- 30、查詢同名同性學生名單，並統計同名人數 
279 select a.s_name,a.s_sex,count(*) from student a  JOIN 
280                     student b on a.s_id !=b.s_id and a.s_name = b.s_name and a.s_sex = b.s_sex
281         GROUP BY a.s_name,a.s_sex
282 -- 31、查詢1990年出生的學生名單
283  select s_name from student where s_birth like '1990%'
284 -- 32、查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列 
285 select c_id,ROUND(AVG(s_score),2) as avg_score from score GROUP BY c_id ORDER BY avg_score DESC,c_id ASC
286 -- 33、查詢平均成績大於等於85的所有學生的學號、姓名和平均成績 
287     select a.s_id,b.s_name,ROUND(avg(a.s_score),2) as avg_score from score a
288         left join student b on a.s_id=b.s_id GROUP BY s_id HAVING avg_score>=85
289 -- 34、查詢課程名稱為"數學"，且分數低於60的學生姓名和分數 
290  
291         select a.s_name,b.s_score from score b LEFT JOIN student a on a.s_id=b.s_id where b.c_id=(
292                     select c_id from course where c_name ='數學') and b.s_score<60
293 
294  
295 -- 35、查詢所有學生的課程及分數情況； 
296 select a.s_id,a.s_name,
297                     SUM(case c.c_name when '語文' then b.s_score else 0 end) as '語文',
298                     SUM(case c.c_name when '數學' then b.s_score else 0 end) as '數學',
299                     SUM(case c.c_name when '英語' then b.s_score else 0 end) as '英語',
300                     SUM(b.s_score) as  '總分'
301         from student a left join score b on a.s_id = b.s_id 
302         left join course c on b.c_id = c.c_id 
303         GROUP BY a.s_id,a.s_name
304  -- 36、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數；
305    select a.s_name,b.c_name,c.s_score from course b left join score c on b.c_id = c.c_id
306                 left join student a on a.s_id=c.s_id where c.s_score>=70
307 -- 37、查詢不及格的課程
308  select a.s_id,a.c_id,b.c_name,a.s_score from score a left join course b on a.c_id = b.c_id
309             where a.s_score<60 
310 --38、查詢課程編號為01且課程成績在80分以上的學生的學號和姓名；
311 select a.s_id,b.s_name from score a LEFT JOIN student b on a.s_id = b.s_id
312             where a.c_id = '01' and a.s_score>80
313 -- 39、求每門課程的學生人數 
314         select count(*) from score GROUP BY c_id;
315 
316 -- 40、查詢選修"張三"老師所授課程的學生中，成績最高的學生資訊及其成績
317 -- 查詢老師id   
318         
319 select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='張三'
320         -- 查詢最高分（可能有相同分數）
321         select MAX(s_score) from score where c_id='02'
322         -- 查詢資訊
323         select a.*,b.s_score,b.c_id,c.c_name from student a
324             LEFT JOIN score b on a.s_id = b.s_id
325             LEFT JOIN course c on b.c_id=c.c_id
326             where b.c_id =(select c_id from course c,teacher d where c.t_id=d.t_id and d.t_name='張三')
327             and b.s_score in (select MAX(s_score) from score where c_id='02')
328 -- 41、查詢不同課程成績相同的學生的學生編號、課程編號、學生成績 
329 select DISTINCT b.s_id,b.c_id,b.s_score from score a,score b where a.c_id != b.c_id and a.s_score = b.s_score
330 -- 42、查詢每門功成績最好的前兩名 
331 -- 牛逼的寫法
332     select a.s_id,a.c_id,a.s_score from score a
333         where (select COUNT(1) from score b where b.c_id=a.c_id and b.s_score>=a.s_score)<=2 ORDER BY a.c_id
334 -- 43、統計每門課程的學生選修人數（超過5人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列  
335         select c_id,count(*) as total from score GROUP BY c_id HAVING total>5 ORDER BY total,c_id ASC
336 -- 44、檢索至少選修兩門課程的學生學號 
337         select s_id,count(*) as sel from score GROUP BY s_id HAVING sel>=2
338 -- 45、查詢選修了全部課程的學生資訊  
339 select * from student where s_id in(        
340             select s_id from score GROUP BY s_id HAVING count(*)=(select count(*) from course))
341 --46、查詢各學生的年齡
342 -- 按照出生日期來算，當前月日 < 出生年月的月日則，年齡減一
343  
344     select s_birth,(DATE_FORMAT(NOW(),'%Y')-DATE_FORMAT(s_birth,'%Y') - 
345                 (case when DATE_FORMAT(NOW(),'%m%d')>DATE_FORMAT(s_birth,'%m%d') then 0 else 1 end)) as age
346         from student;
347 -- 47、查詢本週過生日的學生
348     
349 select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))=WEEK(s_birth)
350     select * from student where YEARWEEK(s_birth)=YEARWEEK(DATE_FORMAT(NOW(),'%Y%m%d'))
351  
352     select WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))
353 -- 48、查詢下週過生日的學生
354     select * from student where WEEK(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =WEEK(s_birth)
355 -- 49、查詢本月過生日的學生
356     select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d')) =MONTH(s_birth)
357 -- 50、查詢下月過生日的學生
358     select * from student where MONTH(DATE_FORMAT(NOW(),'%Y%m%d'))+1 =MONTH(s_birth)
359