mysql update current data - mysql

Question

I'd like to increase/decrease upVote column value by 1 depending on isUpVote boolean value. I get this error when I try the code below. postID and upVote values are all integer.
MySQLdb._exceptions.ProgrammingError: (1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'upVote': 0}' - 1 WHERE postID = '2'' at line 1")
#app.route('/posts/upvote', methods=['GET', 'PATCH'])
def upvote_post():
if request.method == 'PATCH':
data = request.get_json()
print(data)
postID = data['postID']
isUpVote = data['isUpVote']
cur = mysql.connection.cursor()
cur.execute("SELECT upVote FROM posts WHERE postID = '{}'".format(postID))
current_upVote = cur.fetchone()
if isUpVote:
cur.execute("UPDATE posts SET upVote = '{0}' + 1 WHERE postID = '{1}'".format(current_upVote, postID))
else:
cur.execute("UPDATE posts SET upVote = '{0}' - 1 WHERE postID = '{1}'".format(current_upVote, postID))
How should I fix the error?
And I'd like to know if there's a simpler way to update the upVote value in one line without defining current_upVote variable.

Answer 1

You don't need the select Query at all, you can simple add or subtract 1 of the current value
#app.route('/posts/upvote', methods=['GET', 'PATCH'])
def upvote_post():
if request.method == 'PATCH':
data = request.get_json()
print(data)
postID = data['postID']
isUpVote = data['isUpVote']
cur = mysql.connection.cursor()
if isUpVote:
cur.execute("UPDATE posts SET upVote = upVote + 1 WHERE postID = '{0}'".format( postID))
else:
cur.execute("UPDATE posts SET upVote = upVote - 1 WHERE postID = '{0}'".format( postID))

Answer 2

current_upvote is a dictionary containing the row that you fetched. You need to extract the value from it.
You can also do the arithmetic in Python, then just do a single query to update.
You should use parameters rather than string formatting to substitute into queries.
cur.execute("SELECT upVote FROM posts WHERE postID = %s", (postID,))
current_upVote = cur.fetchone()
if isUpvote:
vote = current_upVote['upVote'] + 1
else:
vote = current_upVote['upVote'] - 1
cur.execute("UPDATE posts SET upVote = %s WHERE postID = %s", (vote, postID))
However, the best way to do it is nbk's answer. I only posted this to explain why your code didn't work, and also to show the proper use of parameters.