Impossibile utilizzare i valori None (NULL) in python mysql.connector nell'istruzione INSERT preparata

Question

Quando si cerca di utilizzare il cursore preparato e inserire NULL valori mysql.connector segnala un errore:

mysql.Error: 1210 (HY000): Incorrect arguments to mysqld_stmt_execute 

Ecco un codice che mostra esattamente questo.

from __future__ import print_function 
import mysql.connector 

def execsql(cursor, sqlstmt): 
    try: 
     cursor.execute(sqlstmt) 
    except mysql.connector.Error as e: 
     print("mysql.Error: %s" % e) 
    print(cursor._executed, '\n') 


def execsqlwithparams(cursor, sqlstmt, params): 
    try: 
     cursor.execute(sqlstmt, params) 
    except mysql.connector.Error as e: 
     print("mysql.Error: %s" % e) 
    print(cursor._executed, "params:", params, '\n') 


def main(): 
    print("mysql.connector.__version__", mysql.connector.__version__) 
    db = mysql.connector.connect(db="test") 
    print("mysql.db. get server version", db.get_server_version()) 
    c1 = db.cursor() 
    c2 = db.cursor(prepared=False) 
    c3 = db.cursor(prepared=True) 

    execsql(c1, "drop table if exists test1") 
    execsql(c1, "create table test1 (col1 int not null, col2 int null, primary key(col1))") 

    print("insert with pure SQL") 
    execsql(c1, "insert into test1(col1,col2) values (1, 1)") 
    execsql(c1, "insert into test1(col1,col2) values (2, NULL)") 

    print("insert with prepared statement format %s") 
    sql = "insert into test1(col1,col2) values (%s, %s)" 
    execsql(c2, sql) 
    execsqlwithparams(c2, sql, (20, 20)) 
    execsqlwithparams(c2, sql, (21, None)) 

    print("insert with prepared statement format %s using prepared cursor") 
    sql = "insert into test1(col1,col2) values (%s, %s)" 
    execsql(c3, sql) 
    execsqlwithparams(c3, sql, (30, 30)) 
    execsqlwithparams(c3, sql, (31, None)) 

    execsql(c1, "select * from test1") 
    row = c1.fetchone() 
    while row: 
     print(row) 
     row = c1.fetchone() 
    db.close() 


if __name__ == '__main__': 
    status = main() 

L'output è simile al seguente:

mysql.connector.__version__ 1.2.2 
mysql.db. get server version (5, 5, 37) 
drop table if exists test1 

create table test1 (col1 int not null, col2 int null, primary key(col1)) 

insert with pure SQL 
insert into test1(col1,col2) values (1, 1) 
insert into test1(col1,col2) values (2, NULL) 

insert with prepared statement format %s 
mysql.Error: 1064 (42000): 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 '%s, %s)' at line 1 
insert into test1(col1,col2) values (%s, %s) 
insert into test1(col1,col2) values (20, 20) params: (20, 20) 
insert into test1(col1,col2) values (21, NULL) params: (21, None) 

insert with prepared statement format %s using prepared cursor 
insert into test1(col1,col2) values (%s, %s) 
insert into test1(col1,col2) values (%s, %s) params: (30, 30) 

mysql.Error: 1210 (HY000): Incorrect arguments to mysqld_stmt_execute 
insert into test1(col1,col2) values (%s, %s) params: (31, None) 

select * from test1 

(1, 1) 
(2, None) 
(20, 20) 
(21, None) 
(30, 30) 

Il risultato inatteso è questo:

mysql.Error: 1210 (HY000): Incorrect arguments to mysqld_stmt_execute 
insert into test1(col1,col2) values (%s, %s) params: (31, None) 

E manca fila (31, None) dal database.

Answer 1

Il tuo problema relativo a Nessuno superato nell'ultimo caso può essere causato dal fatto che il Nessuno non viene interpretato come il tipo definito nella tabella.