SQLite database for sensor data in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is SQLite and why is it suitable for storing sensor data on a Raspberry Pi?

SQLite is a lightweight, file-based database engine. It is suitable for Raspberry Pi because it requires no server setup, uses minimal resources, and stores data locally, making it ideal for small sensor data projects.

beginner

Which Python module is commonly used to interact with SQLite databases on Raspberry Pi?

The 'sqlite3' module is commonly used in Python to create, read, update, and delete data in SQLite databases on Raspberry Pi.

beginner

What is the purpose of the SQL command 'CREATE TABLE' in the context of sensor data?

'CREATE TABLE' defines a new table structure in the database to store sensor readings, specifying columns like timestamp, sensor type, and value.

beginner

Why should sensor data entries include a timestamp?

Timestamps record when each sensor reading was taken, allowing tracking of data over time and analysis of trends or events.

beginner

How do you insert a new sensor reading into an SQLite database using Python?

Use a SQL 'INSERT INTO' statement with parameters in Python's sqlite3 module, then commit the transaction to save the data.

Which command creates a new table in an SQLite database?

A INSERT INTO

B SELECT

C CREATE TABLE

D UPDATE

'CREATE TABLE' is used to define a new table structure in the database.

What Python module do you use to work with SQLite on Raspberry Pi?

A os

B pandas

C math

D sqlite3

The 'sqlite3' module provides functions to interact with SQLite databases.

Why is it important to include a timestamp with sensor data?

A To increase database size

B To know when the data was recorded

C To make data unreadable

D To slow down data insertion

Timestamps help track when each sensor reading was taken.

Which SQL command adds new data to a table?

A INSERT INTO

B CREATE TABLE

C DELETE

D DROP TABLE

'INSERT INTO' adds new rows of data to a table.

What is a key advantage of SQLite on Raspberry Pi for sensor data?

A No need for a separate database server

B Requires internet connection

C Only works with large data sets

D Needs complex setup

SQLite stores data in a file and does not require a separate server.

Explain how to set up an SQLite database on Raspberry Pi to store sensor data.

Think about the steps from Python code to saving data.

Describe why SQLite is a good choice for logging sensor data on a Raspberry Pi.

Consider resource use and simplicity.

Practice

1. What is the main purpose of using SQLite on a Raspberry Pi for sensor data?

easy

A. To send sensor data directly to the cloud

B. To control the sensor hardware directly

C. To store sensor readings locally without needing a separate database server

D. To display sensor data on a web page automatically

Solution

1. Step 1: Understand SQLite's role on Raspberry Pi

   SQLite is a lightweight database that runs locally without needing a separate server.

2. Step 2: Connect SQLite to sensor data storage

   It stores sensor readings on the Raspberry Pi itself, making data management easy and offline.

3. Final Answer:

   To store sensor readings locally without needing a separate database server -> Option C

4. Quick Check:

   SQLite stores data locally = B [OK]

Hint: SQLite stores data locally on Pi, no extra server needed [OK]

Common Mistakes:

• Confusing SQLite with cloud services
• Thinking SQLite controls hardware
• Assuming SQLite automatically displays data

2. Which of the following is the correct Python code snippet to create a table named sensors with columns id (integer primary key), name (text), and value (real)?

easy

A. cursor.execute('CREATE TABLE sensors (id INTEGER PRIMARY KEY, name TEXT, value REAL)')

B. cursor.execute('CREATE sensors TABLE (id INT, name STRING, value FLOAT)')

C. cursor.execute('MAKE TABLE sensors (id PRIMARY KEY, name TEXT, value REAL)')

D. cursor.execute('CREATE TABLE sensors id INTEGER, name TEXT, value REAL')

Solution

1. Step 1: Check SQL syntax for table creation

   The correct SQL command is CREATE TABLE followed by table name and column definitions in parentheses.

2. Step 2: Match Python sqlite3 syntax

   Python uses cursor.execute() with a valid SQL string. cursor.execute('CREATE TABLE sensors (id INTEGER PRIMARY KEY, name TEXT, value REAL)') matches correct SQL and Python syntax.

3. Final Answer:

   cursor.execute('CREATE TABLE sensors (id INTEGER PRIMARY KEY, name TEXT, value REAL)') -> Option A

4. Quick Check:

   Correct SQL CREATE TABLE syntax = D [OK]

Hint: Use 'CREATE TABLE table_name (columns)' inside cursor.execute() [OK]

Common Mistakes:

• Using wrong SQL keywords like MAKE TABLE
• Incorrect column types like STRING instead of TEXT
• Missing parentheses around columns

3. Given this Python code snippet using sqlite3 on Raspberry Pi:

import sqlite3
conn = sqlite3.connect('data.db')
cursor = conn.cursor()
cursor.execute('CREATE TABLE IF NOT EXISTS sensors (name TEXT, value REAL)')
cursor.execute("INSERT INTO sensors VALUES ('temp', 23.5)")
cursor.execute('SELECT * FROM sensors')
rows = cursor.fetchall()
print(rows)

What will be the output?

medium

A. [('temp', 23.5)]

B. []

C. SyntaxError

D. None

Solution

1. Step 1: Understand table creation and insertion

   The table 'sensors' is created if not exists, then a row ('temp', 23.5) is inserted.

2. Step 2: Fetch all rows and print

   The SELECT query fetches all rows, which includes the inserted row, so print outputs [('temp', 23.5)].

3. Final Answer:

   [('temp', 23.5)] -> Option A

4. Quick Check:

   Inserted row fetched = [('temp', 23.5)] [OK]

Hint: Inserted data appears in fetchall() output as list of tuples [OK]

Common Mistakes:

• Forgetting to insert data before SELECT
• Expecting empty list if table exists
• Confusing fetchall() output format

4. This Python code tries to insert sensor data but causes an error:

cursor.execute('CREATE TABLE sensors (name TEXT, value REAL)')
cursor.execute('INSERT INTO sensors (name, value) VALUES (?, ?)', ('humidity'))
conn.commit()

What is the error and how to fix it?

medium

A. Error: SQL syntax error; fix by removing parentheses in VALUES

B. Error: Missing second value in tuple; fix by adding a second value like ('humidity', 45.0)

C. Error: Table sensors does not exist; fix by creating table first

D. Error: commit() missing; fix by adding conn.commit()

Solution

1. Step 1: Identify parameter mismatch in INSERT

   The VALUES clause expects two values, but only one ('humidity') is given as a tuple missing a second element.

2. Step 2: Fix by providing both values

   Provide a tuple with two elements, e.g., ('humidity', 45.0), to match the two columns.

3. Final Answer:

   Error: Missing second value in tuple; fix by adding a second value like ('humidity', 45.0) -> Option B

4. Quick Check:

   Parameter count matches columns = C [OK]

Hint: Tuple for parameters must match number of placeholders [OK]

Common Mistakes:

• Passing single string instead of tuple with two values
• Ignoring commit() after insert
• Wrong SQL syntax in INSERT statement

5. You want to store sensor readings with a timestamp in SQLite on Raspberry Pi. Which table schema and insertion code correctly store sensor name, value, and current time using Python's sqlite3?

hard

A. CREATE TABLE readings (name TEXT, value REAL, time TEXT); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, 'CURRENT_TIMESTAMP')")

B. CREATE TABLE readings (name TEXT, value REAL, time INTEGER); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, CURRENT_TIMESTAMP)")

C. CREATE TABLE readings (name TEXT, value REAL, time INTEGER); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, datetime('now'))")

D. CREATE TABLE readings (name TEXT, value REAL, time TEXT); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, datetime('now', 'localtime'))")

Solution

1. Step 1: Choose correct table schema for timestamp

   Use TEXT type for time column to store datetime strings, which SQLite supports well.

2. Step 2: Insert current local time correctly

   Use SQLite function datetime('now', 'localtime') to get current local timestamp as text.

3. Step 3: Match insertion code with schema

   CREATE TABLE readings (name TEXT, value REAL, time TEXT); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, datetime('now', 'localtime'))") uses TEXT time column and inserts with datetime('now', 'localtime'), which is correct.

4. Final Answer:

   CREATE TABLE readings (name TEXT, value REAL, time TEXT); cursor.execute("INSERT INTO readings VALUES ('temp', 22.1, datetime('now', 'localtime'))") -> Option D

5. Quick Check:

   Local timestamp stored as TEXT = A [OK]

Hint: Use datetime('now', 'localtime') for current local time in SQLite [OK]

Common Mistakes:

• Using CURRENT_TIMESTAMP without quotes in Python
• Storing time as INTEGER without conversion
• Ignoring localtime adjustment for timestamps