Got it, let's fix that annoying truncation warning you're seeing when using cursor.execute() with MySQL in Python. The issue ties into mismatched data types, proper use of MySQL's date functions, and handling your ort (string) and messwert (float) columns correctly.

First, Understand the Warning #

The Data truncated for column 'col1' error almost always means there's a mismatch between the data you're inserting and the column's defined type or length. For date columns like col1, this usually happens if you're passing a string-formatted date instead of a properly typed date value, or using a format MySQL doesn't recognize. For your other columns, it could be a string that's too long for ort or a float value being mishandled as a string.

Step 1: Use MySQL's Built-in Date Functions Directly #

Stop trying to format dates in Python and pass them as strings—let MySQL handle this natively! CURRENT_DATE() and NOW() are MySQL functions that return perfectly formatted values matching DATE/DATETIME column types. Just write them directly in your SQL query, don't pass them as parameters.

Step 2: Use Parameterized Queries for Your Typed Columns #

Parameterized queries let Python's DB-API automatically convert your Python types to MySQL-compatible values, eliminating truncation risks and SQL injection at the same time.

Here's a concrete example:

# Assume your table has columns: col1 (DATE), ort (VARCHAR), messwert (FLOAT), created_at (DATETIME)
query = """
INSERT INTO your_table_name (col1, ort, messwert, created_at)
VALUES (CURRENT_DATE(), %s, %s, NOW())
"""

# Pass your values as a tuple (ort is string, messwert is float)
ort_value = "Berlin"  # Make sure this length fits your VARCHAR column's defined length!
messwert_value = 23.7

cursor.execute(query, (ort_value, messwert_value))

Key Checks to Avoid Truncation #

• For col1 (date column): Ensure the column type matches the function you're using. CURRENT_DATE() returns a DATE type (YYYY-MM-DD), so use it with DATE columns. If col1 is DATETIME, use NOW() or CURRENT_TIMESTAMP() instead.
• For ort (string column): Double-check the column's defined length (e.g., VARCHAR(50)). If your ort_value is longer than that, you'll get truncation. Either shorten the string in your code or alter the column to allow longer values.
• For messwert (float column): Always pass a Python float type, not a string. If you're reading the value as a string (e.g., from user input), convert it to a float first with float(messwert_str) before passing it to execute().

If You Must Use Python-Generated Dates #

If you need to insert a specific date (not the current one), format it as an ISO string (YYYY-MM-DD) which MySQL recognizes perfectly, and pass it as a parameter:

from datetime import date

specific_date = date(2024, 5, 20).isoformat()
query = "INSERT INTO your_table (col1) VALUES (%s)"
cursor.execute(query, (specific_date,))

This avoids any formatting mismatches that cause truncation.

内容的提问来源于stack exchange，提问作者Kai H.