Why Does Pandas\' to_sql Fail with a \'Wrong Number of Arguments\' Error When Writing to MySQL?

Troubleshooting Writing to MySQL Database with Pandas Using SQLAlchemy's to_sql

When attempting to write a Pandas DataFrame to a MySQL database using SQLAlchemy's to_sql method, you may encounter an error that resembles:

DatabaseError: Execution failed on sql 'SELECT name FROM sqlite_master
WHERE type='table' AND name=?;': Wrong number of arguments during
string formatting

This error indicates a discrepancy in the SQL query being executed. Interestingly, it suggests an attempt to select from a SQLite database instead of MySQL.

To rectify this issue and establish the correct connection with MySQL using the SQLAlchemy engine and mysqlconnector, follow these steps:

• Utilize the engine object directly as the connection parameter for to_sql:

import pandas as pd
import mysql.connector
from sqlalchemy import create_engine

# Create SQLAlchemy engine
engine = create_engine('mysql+mysqlconnector://[user]:[pass]@[host]:[port]/[schema]', echo=False)

# Read and write using the engine connection
data = pd.read_sql('SELECT * FROM sample_table', engine)
data.to_sql(name='sample_table2', con=engine, if_exists='append', index=False)

This modification ensures that the connection used for both reading and writing is the SQLAlchemy engine connected to MySQL. It eliminates the initial attempt to use a raw connection, which may have triggered the SQLite-related error.

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