Sqlite3 Tutorial Query Python Fixed |work|

SQLite3 Tutorial: Python Database Query Guide

Table of Contents

1. Introduction to SQLite3
2. Setup and Installation
3. Basic Database Operations
4. CRUD Operations
5. Querying Data
6. Advanced Queries
7. Best Practices
8. Common Errors and Solutions

• For large binary data, store files on disk and save paths in DB.

Usage

all_users = query_all_users() for user in all_users: print(user)

7. DELETE Queries

def delete_user(user_id):
    # First delete related posts (or use ON DELETE CASCADE)
    cursor.execute("DELETE FROM posts WHERE user_id = ?", (user_id,))
    cursor.execute("DELETE FROM users WHERE id = ?", (user_id,))
    conn.commit()
    return cursor.rowcount
Error 4: Fetching returns [] or None
Cause: No rows match, or you forgot to fetch.

Fix: Use fetchone() for single row, fetchall() for all. Check your WHERE clause. sqlite3 tutorial query python fixed
5) Querying
# fetch one
cur.execute("SELECT id, name, email FROM users WHERE email = ?", ("alice@example.com",))
row = cur.fetchone()
if row:
    id, name, email = row
cursor.execute("INSERT OR IGNORE INTO users (name, email) VALUES (?, ?)", ("Bob", "bob@example.com"))

return rows_deleted

def init_db():
with sqlite3.connect(DB_NAME) as conn:
cursor = conn.cursor()
cursor.execute("""
CREATE TABLE IF NOT EXISTS tasks (
id INTEGER PRIMARY KEY AUTOINCREMENT,
title TEXT NOT NULL,
completed INTEGER DEFAULT 0
)
""") SQLite3 Tutorial: Python Database Query Guide Table of