在python中遍历MySQL的问题

Question

I just started learning python and am trying out projects. I'm having a with my python code. What I want to do is to go through the rows in my table one after another and perform a specific task on each row. With an example, I have rows with multiple columns and three of the columns are con_access, exam and total. Now I want to get sum of the values in con_access and exam columns and then put it in the total column. This calculation should done one by one. The problem that am having is that the program goes to the last row, takes the total variable and populate every other with it

Below is my code

def result_total():
    mdb = mysql.connector.connect(
        host="localhost",
        user="root",
        passwd="**************",
        database="majesty"
    )

    mycursor = mdb.cursor()
    # mycursor.execute("SELECT con_access, exam FROM students")
    mycursor.execute("SELECT CAST(con_access AS UNSIGNED) as con_access, CAST(exam AS UNSIGNED) as exam FROM students")
    rows = mycursor.fetchall()
    for row in rows:
        if row:
            total = row['con_access'] + row['exam']
            sql = "UPDATE students SET total = {}".format(total)
            mycursor.execute(sql)
            mdb.commit()

Answer 1

find total like below

total = row['con_access'] + row['exam']

If your datatype of con_access and exam in mysql table is varchar, you should cast it. Change the select query as follows.

SELECT CAST(con_access AS UNSIGNED) as con_access, CAST(exam AS UNSIGNED) as exam FROM students