mysql - Mysql converts varchar to year while update

Question

I have a query for updating varchar time field and I don't want to keep them in DATE format. My string date format is yyyy-mm-dd is 2018-05-13.

query = "UPDATE SchedulePlaylist
    SET start = %s ,end = %s
    WHERE playlist_id = %s AND schedule_id = %s" % (
                str(start), str(end), playlist_id, schedule_id)

how can I prevent this conversion. I am using python and flask_mysqldb connector

Answer 1

The proper approach is to use parameters to pass the values in. This could get awkward, because of the date/string issues.

The naive solution in your case is to add single quotes around values:

query = "UPDATE SchedulePlaylist
    SET start = '%s', end = '%s'
    WHERE playlist_id = %s AND schedule_id = %s" % (
                str(start), str(end), playlist_id, schedule_id)

Your code is treating 2018-04-30 as arithmetic and producing 1984. The single quote cause them to be represented as a string.

What you should really do is fix the table, so the columns have the correct type. A string stored as YYYY-MM-DD is a reasonable type if you have to store the date as a string. Otherwise use date. However, that doesn't fix your update problem.

The better solution is to use parameters, and that is simple. The parameters go in the execute call:

query = """
UPDATE SchedulePlaylist
    SET start = ?, end = ?
    WHERE playlist_id = ? AND schedule_id = ?
""";

cursor.execute(query, (str(start), str(end), playlist_id, schedule_id));