如何使用python返回mysql查询结果

Question

查询结果和下面的预期输出。

+------+----------+ 
| YEAR | MAX_TEMP | 
+------+----------+ 
| 1990 |  603 | 
| 1991 |  605 | 
+------+----------+ 

这是我的代码。在没有记录的输出中（即2）。我怎样才能让它显示整个表格？

import MySQLdb 

    conn = MySQLdb.connect("localhost","root","root","vkp") 
    cursor = conn.cursor() 
    print ("Opened database successfully"); 

    def select(): 
     #database_conn() 
     print ("inside select") 
     a = cursor.execute("SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from TEMP_DATA WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt); SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from MAX_TEMP9293 WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt)") 

     return a 
     conn.commit() 
     conn.close 
    a = select() 
    print (a) 

Answer 1

你错过fetchall

所有你正在做的是返回结果的数量，而不是实际的结果本身。

更改此：

a = cursor.execute("SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from TEMP_DATA WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt); SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from MAX_TEMP9293 WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt)") 

要这样：

cursor.execute("SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from TEMP_DATA WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt); SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from MAX_TEMP9293 WHERE air_temp != 9999 AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') GROUP BY year(dt)") 

a = cursor.fetchall() 

还没有为commit存在的点。您不会修改此函数中实际表格中的任何数据，这是它的目的。

Answer 2

1. 代码中的缩进关闭;按照书面形式，您的代码不会编译（您可能需要更正提交问题时的格式）。

2. @aws_apprentice是正确的。您应该在代码中包含fetchall。我会写这样的：

   import MySQLdb 
   
   conn = MySQLdb.connect("localhost","root","root","vkp") 
   curs = conn.cursor() 
   print ("Opened database successfully"); 
   
   def select(): 
       #database_conn() 
       print ("inside select") 
       curs.execute(""" 
        SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP 
        FROM TEMP_DATA 
        WHERE air_temp != 9999 
        AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') 
        GROUP BY year(dt); 
        SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP 
        FROM MAX_TEMP9293 
        WHERE air_temp != 9999 
        AND (quality_at = '0' || quality_at = '1' || quality_at = '4' || quality_at = '5' || quality_at = '9') 
        GROUP BY year(dt) 
        """ 
        ) 
   
       result = curs.fetchall() 
   
       return result 
   
   a = select() 
   conn.close() 
   print(a) 
   

3. 我不是100％肯定，但我不认为MySQLdb的将漂亮的打印输出，你表示你希望它，因为这个代码写。图书馆可能有一些方法可以做到这一点;可能值得进一步研究。上面的代码将输出包含您的数据的元组列表（我认为;未经测试）。

Answer 3

我设法得到输出，这是代码被使用。

databasename = 'vkp' 
host = 'localhost' 
user = 'root' 
password = 'root' 

#mysql connection 
conn = MySQLdb.connect(host,user,password,databasename) 
cursor = conn.cursor() 

#defining sql select statements 
print ("Opened database successfully"); 
sql = "SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from TEMP_DATA WHERE air_temp != 9999 GROUP BY year(dt)" 
sql1 = "SELECT year(dt) AS YEAR, max(air_temp) AS MAX_TEMP from MAX_TEMP9293 WHERE air_temp != 9999 GROUP BY year(dt)" 
#list for storing sql queries 
list = [sql,sql1] 

#function for executing select statements 
def select(): 
    #iterating for loop 
    for l in list: 
     #executing query 
     cursor.execute(l) 
     max = cursor.fetchall() 
     #printing max temp for years 
     print(max[0]) 
     print(max[1])