Python Tutorial

Python MySQL - Insert Into

Add rows safely with parameterized queries, and insert many rows at once.

Insert a Single Row

Use placeholders (%s) and pass the values separately — never build SQL with string formatting. After a write you must commit() to save it.

import mysql.connector

conn = mysql.connector.connect(
    host="localhost", user="root", password="secret", database="mydatabase")
cursor = conn.cursor()

sql = "INSERT INTO customers (name, address) VALUES (%s, %s)"
values = ("John", "Highway 21")
cursor.execute(sql, values)

conn.commit()                       # save the change
print(cursor.rowcount, "record inserted.")   # 1 record inserted.

Placeholders are always %s regardless of the Python type — do not add quotes around them. This is what prevents SQL injection.

Why Parameterized Queries Matter

Building SQL by concatenation lets malicious input change your query — a SQL injection attack. The driver escapes parameterized values for you.

# DANGEROUS - never do this:
# cursor.execute("INSERT INTO customers (name) VALUES ('" + name + "')")

# SAFE:
cursor.execute("INSERT INTO customers (name) VALUES (%s)", (name,))

Insert Many Rows with executemany

Passing a list of tuples to executemany is far faster than a loop of single inserts.

sql = "INSERT INTO customers (name, address) VALUES (%s, %s)"
rows = [
    ("Peter", "Lowstreet 4"),
    ("Amy",   "Apple st 652"),
    ("Hannah","Mountain 21"),
]
cursor.executemany(sql, rows)
conn.commit()
print(cursor.rowcount, "records inserted.")   # 3 records inserted.

Get the Inserted ID

After inserting into a table with an auto-increment key, read the new id from cursor.lastrowid.

cursor.execute("INSERT INTO customers (name) VALUES (%s)", ("Mia",))
conn.commit()
print("New id:", cursor.lastrowid)

Transactions: All or Nothing

Group related writes so they either all succeed or all roll back, keeping data consistent.

try:
    cursor.execute("INSERT INTO customers (name) VALUES (%s)", ("A",))
    cursor.execute("INSERT INTO customers (name) VALUES (%s)", ("B",))
    conn.commit()                   # commit both together
except mysql.connector.Error:
    conn.rollback()                 # undo everything on any failure
    raise

Best Practices

  • Always use %s placeholders — never string formatting.
  • Call commit() after inserts/updates/deletes, or nothing is saved.
  • Use executemany for bulk inserts.
  • Wrap multi-step writes in a try/except with rollback().

Try It Yourself

Exercise 1: What is wrong with "INSERT INTO t (name) VALUES ('" + name + "')"?

Show solution

It is vulnerable to SQL injection. Use a placeholder instead: cursor.execute("INSERT INTO t (name) VALUES (%s)", (name,)).

Exercise 2: After inserting rows, what must you call to save them?

Show solution

conn.commit() — without it the changes are rolled back when the connection closes.

📘 Real-World Deep Dive

Knowing <strong>MySQL Insert (MySQL)</strong> well is what turns MySQL from a curiosity into a daily tool — you'll reach for it in nearly every real project.

Real-Life Scenario

An end-to-end usage of MySQL Insert that you'd actually see in a data pipeline or analytics notebook.

Real-Life Example

import mysql.connector
conn = mysql.connector.connect(database="shop")
cur = conn.cursor()
cur.executemany(
    "INSERT INTO users (name, email) VALUES (%s, %s)",
    [("Ada", "ada@x"), ("Bo", "bo@x")],
)
conn.commit(); print("rows:", cur.rowcount)

Expected Output

(see source)

Common mistakes

  • Reading with the default cursor returns tuples — switch to DictCursor for named access.
  • Strings without parameter binding produce SQL-injection holes — never use f-strings in queries.
  • Connecting through a long-lived daemon pool: make sure pool_reset_connection is on to avoid session state leakage.
  • Treating MySQL Insert as a black box without reading the docs — the API has subtle defaults that bite when you scale.

🚀 Performance & Best Practices

  • Use prepared statements (cursor.executemany) for bulk inserts.
  • Fetch with cursor.fetchmany(1000) in streams instead of fetchall().
  • Use pymysql's server-side cursors for very large result sets.
  • When working with MySQL, prefer vectorised / batched operations over Python loops.

🧪 Try It Yourself

  1. Reproduce the snippet on a representative slice of your own data.
  2. Profile the snippet with cProfile or timeit and find the single biggest improvement.
  3. Generalise the snippet into a small, reusable function you can drop into future projects.

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