17.Sqlite 数据查询

Posted 2021-04-30 KidsCode

本节目的:

学会Sqlite数据库中的数据查询方法。

步骤:

步骤1: 采用用SqliteStudio查询数据:

A.通过数据界面 B.使用Sql语句查询数据

步骤2: 启动SublimeText,编写Py文件如下:

三段SelectDemo 如下:

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import sqlite3  
 
db_filename = 'htxx.db'
conn=sqlite3.connect(db_filename)
cursor = conn.cursor()
rows=cursor.execute('''select avg(score) from class6 where name = 'ma' ''')
for row in rows.fetchone():        
       print(row)
cursor.close()
conn.close()
 
 
 
# with sqlite3.connect(db_filename) as conn:  
#     cursor = conn.cursor()
#     rows=cursor.execute('''select avg(score) from class6 where name = 'ma' ''')
#     for row in rows.fetchone():        
#            print(row)

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import sqlite3  
      
db_filename = 'htxx.db'   
with sqlite3.connect(db_filename) as conn:  
    cursor = conn.cursor()        
    cursor.execute('''select id,name,course,score from class6 where name = 'ma' ''')        
    for row in cursor.fetchall():  
        id,name,course,score=row  
        print('id=%d name=%s course=%s score=%f'%(id,name,course,score)) 
--------------------------------

import sqlite3  
      
db_filename = 'htxx.db'  
course_count=0   
avgscore=0   
with sqlite3.connect(db_filename) as conn:  
    cursor = conn.cursor()        
    cursor.execute('''select id,name,course,score from class6 where name = 'ma' ''')        
    for row in cursor.fetchall():
        (id, name,course,score)=row  
        print('id=%d name=%s course=%s score=%f'%(id,name,course,score))
        avgscore +=score
        course_count+=1
avgscore=avgscore/course_count
print('average=%f'%avgscore)

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