Retrieve SQL query using python every few seconds

Question

I am trying to retrieve an ongoing insert script from SQL Server using python and output the data one by one every 3seconds. Please help a noobie here!

However, I am getting the error message:

Nothing in database
name 'prev_id' is not defined

Any ideas why?

import time
sql_conn = connectSQLServer('ODBC Driver 13 for SQL Server', 'DESKTOP\SQLEXPRESS', 'display')

mycursor = sql_conn.cursor()
global prev_id
a = 0
d = { 'x': [], 'y': [] ,'z': []  , 'a':[] }
while True:
    try:
        time.sleep(3)
        a=a+1
        print(a)
        sql = "SELECT ID,position ,action ,sync FROM dbo.data2 WHERE ID > %s" % (prev_id)
        mycursor.execute(sql) 
        myresult = mycursor.fetchall()
        #d = { 'x': [], 'y': [] }
        for x in myresult:
            print(x)
            prev_id = x[0]
            d['x'].append(x[0])
            d['y'].append(x[1])
            d['z'].append(x[2])
            d['a'].append(x[3])
        df = pd.DataFrame(d)

    except Exception as error:
        print("Nothing in database\n")
        print(error)
sql_conn.commit()

John Sloper · Accepted Answer · 2020-03-06 07:35:18Z

2

You are getting the error message because you have not assigned any value to the prev_id variable before you use it the first time. Presumably you would want to assign it to 0 or something equivalent.

answered Mar 6, 2020 at 7:35

John Sloper

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