“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 '' at line 1”

Question

I'm trying to execute an insert query. It works when I directly copy and paste it to the mysql command prompt, but fails when I execute it from Python. I'm getting this error with MySQLdb (also tried using _mysql directly and get the same error).

The error is the same as this question, but the answer does not work for my problem (my query is on a single line): MySQL the right syntax to use near '' at line 1 error

query = """INSERT INTO %s(%s) VALUES (%f) ON DUPLICATE KEY UPDATE %s=%f"""%(table_name,measurement_type,value,measurement_type,value)
print query 
cur.execute(query)

Result (it prints the query, which when copied directly into MySQL command prompt executes fine, and then crashes):

INSERT INTO D02CA10B13E5$accelerometer_X(periodic) VALUES (79.000000) ON DUPLICATE KEY UPDATE periodic=79.000000
Traceback (most recent call last):
File "collect_data.py", line 145, in <module>
process_data_array(data_bytes[start:start+sensor_packet_size])
File "collect_data.py", line 105, in process_data_array
record_data(MAC,sensor_name,"X",code_name,X,cur)
File "collect_data.py", line 58, in record_data
cur.execute(query)
File "/usr/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 174, in execute
self.errorhandler(self, exc, value)
File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
_mysql_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 '' at line 1")

I tried turning on profiling because I can't seem be able to access _last_executed from my cursor (something others have suggested). It seems that my cursor does not have this property (was it removed?).

query = """INSERT INTO %s(%s) VALUES (%f) ON DUPLICATE KEY UPDATE %s=%f"""%(table_name,measurement_type,value,measurement_type,value)
print query 
#cur.execute(query)
try:
    cur.execute(query)
except:
    cur.execute('show profiles')
    for row in cur:
        print row
    cur.execute("set profiling = 0")
    exit()

This shows me an incomplete query:

INSERT INTO D02CA10B13E5$accelerometer_X(periodic) VALUES (80.000000) ON DUPLICATE KEY UPDATE periodic=80.000000
(1L, 5.925e-05, 'INSERT INTO D02CA10B13E5')

Some suggest splitting the query into multiple lines (which contradicts the suggestion in the link I posted above). Anyway, it narrows the search to one line (apparently the Python module doesn't like either my table name or column name which are on the third line)

query = "INSERT \nINTO \n%s(%s) \nVALUES \n(%f) \nON \nDUPLICATE \nKEY \nUPDATE %s=%f"%(table_name,measurement_type,value,measurement_type,value)
print query 
cur.execute(query)

Result:

INSERT 
INTO 
D02CA10B13E5$accelerometer_X(periodic) 
VALUES 
(80.000000) 
ON 
DUPLICATE 
KEY 
UPDATE periodic=80.000000
Traceback (most recent call last):
File "collect_data.py", line 145, in <module>
process_data_array(data_bytes[start:start+sensor_packet_size])
File "collect_data.py", line 105, in process_data_array
record_data(MAC,sensor_name,"X",code_name,X,cur)
File "collect_data.py", line 58, in record_data
cur.execute(query)
File "/usr/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 174, in execute
self.errorhandler(self, exc, value)
File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
_mysql_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 '' at line 3")

Again, this query executes fine on MySQL, so I'm not sure what's going on here in Python. Any pointers are appreciated. Thanks!

Answer 1

Ok so '' in the MySQL error apparently referred to a \\0 character that got appended to my table name. This was not visible as you can see for yourself:

>>> print chr(0)

>>> print "hello" + chr(0)
hello

The \\0 character is completely invisible and doesn't get copied onto the clipboard from the terminal (so it worked when pasted onto the MySQL console). Sneaky!

I found this out by comparing string lengths with expected string lengths and finding a difference of 1 character that was invisible to my eyes. The \\0 character came about in my Python code when I read the string (sensor ID) from a socket (the application on the other end was a C program that was appending these \\0 characters).

Hope my answer saves someone else a lot of trouble!