97 lines
2.1 KiB
Markdown
97 lines
2.1 KiB
Markdown
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---
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tags: [python, databases, SQL, SQLite]
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created: Thursday, November 07, 2024
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---
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# Using SQLite with Python
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SQLite is part of the core library, you do not require a separate package
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```py
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import sqlite3
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```
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## Connect to database
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Connect to an existing SQLite `.db` file or create a new database with the same
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command:
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```py
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connection = sqlite3.connect("my_database.db")
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```
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## Disconnect from database
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```python
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connection.close()
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```
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## Querying
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`connect` exposes a `cursor` entity. This is used for executing changes against
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the database file.
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### Example: creating a table
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```python
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CREATE_TAGS_TABLE = """
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CREATE TABLE IF NOT EXISTS tags (
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name TEXT PRIMARY KEY
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)
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"""
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cursor = connection.cursor()
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cursor.execute(CREATE_TAGS_TABLE)
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cursor.commit()
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# Confirm changes
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cursor.execute("SELECT name from sqlite_master WHERE type='table'")
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print(cursor.fetchall())
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# (tags)
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```
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Note that it is necessary to `commit` the changes. The cursor object just stores
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the operation in memory and does not execute until you specifically commit them.
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## Prepared statements and parameterised queries
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### Parameterised queries
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```py
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username = "thomas"
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password = "123"
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cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?",
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(username, password))
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```
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Alternatively, pass the [tuple](Tuples_in_Python.md) directly:
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```python
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login_data = ("thomas", "123")
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cursor.execute("SELECT * FROM users WHERE username = ? AND password = ?",
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login_data)
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```
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### Prepared statements
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> With prepared statements you have to pass in the parameters as a dictionary
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```python
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user_data = {
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"username": "thomas",
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"email": "thomas@email.com"
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}
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cursor.execute("INSERT INTO users (username, email) VALUES (:username, :email)",
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user_data)
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```
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In the example above it so happens that we already have a dictionary we are
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working with. If you want to use a prepared statement and you don't have a
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dictionary already, you will need to construct one as part of the query, e.g:
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```python
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cursor.execute("INSERT INTO table_name (value_one, value_two) VALUES (:value_one, :value_two)", { value_one: 'foo', value_two: 'bar'})
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```
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