Update database using variable from csv file in cx_Oracle

Question

Stuck at a point where I'm getting an error ORA-01036: illegal variable name/number when executing the update command in the Oracle database using cx_Oracle & Python3.6.8.

I'm want to use the value of the variable from the CSV file (db_results.csv) and execute the update command.

The db_results.csv file looks like this:

id, order_id, product, Courier, state
01, ORD987, Keyboard, DHL, TX
02, ORD976, Charger, Blue Dart, NY

My code:

con = cx_Oracle.connect("abc/abc@abc")
cur = con.cursor()

with open(r'D:\db_results.csv') as file:
    next(file)
    for line in file:
        x = line.replace('\n', ' ').replace('\r', '')
        columns = x.split(",")
        y = columns[1]
    SQL = "update inventory set model='301547' where order_id = '?'"
    cur.execute(SQL, y)
    con.commit()
con.close()

Is there any specific syntax for UPDATE to be used in cx_Oracle? Tried to find examples for this, but none found so far.

Answer 1

• ORA-01036 raises due to the wrong type of placeholders for oracle, rather prefer using integers prepended with colons such as :1 , :2

• Don't forget to trim the second placeholder's value in order to get rid of whitespaces wrapping around the value for y

• No need to embed the parameters within the DML, rather convert them to a tuple such as (301547, y)

   ... with open(r'D:\db_results.csv') as file: next(file) for line in file: x = line.replace('\n', ' ').replace('\r', '') columns = x.split(",") y = columns[1] SQL = "UPDATE inventory SET model=:1 WHERE order_id = TRIM(:2)" cur.execute(SQL, (301657, y)) con.commit() con.close()

Answer 2

Calling cur.execute() once for each CSV line (as shown in the accepted answer) will be really slow and cannot be recommended.

Instead, look at using cur.executemany() , similar to the code in the cx_Oracle documentation Loading CSV Files into Oracle Database :

with open('testsp.csv', 'r') as csv_file:
    csv_reader = csv.reader(csv_file, delimiter=',')
    sql = "insert into test (id,name) values (:1, :2)"
    data = []
    for line in csv_reader:
        data.append((line[0], line[1]))
        if len(data) % batch_size == 0:
            cursor.executemany(sql, data)
            data = []
    if data:
        cursor.executemany(sql, data)
    con.commit()

In your case the SQL would be the UPDATE statement, and you just need to construct the data variable with your desired values.