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By Kevin McAleer, 3 Minutes
In Module 4, we will focus on inserting data into SQLite tables and retrieving data using SQL queries. You will learn how to insert records into tables and retrieve specific data using various filtering and sorting techniques.
To add data to a SQLite table, we use the SQL INSERT INTO statement. This statement allows us to specify the table name and provide the values for the columns.
INSERT INTO
# Insert a record into the table connection.execute("INSERT INTO books (title, author, year) VALUES (?, ?, ?)", ("The Great Gatsby", "F. Scott Fitzgerald", 1925))
In this example, we insert a record into the “books” table with the title, author, and year values provided.
Retrieving data from SQLite tables involves using the SQL SELECT statement. This statement allows us to specify which columns we want to retrieve and any conditions or filters for the query.
SELECT
# Retrieve all records from the table result = connection.execute("SELECT * FROM books") data = result.fetchall() # Process the retrieved data for row in data: print(row)
In this code snippet, we retrieve all records from the “books” table and print each row of data.
To retrieve specific data that meets certain conditions, we can use the WHERE clause in SQL queries. The WHERE clause allows us to specify one or more conditions that records must satisfy.
WHERE
# Retrieve records with a specific condition result = connection.execute("SELECT * FROM books WHERE year > ?", (2000,)) data = result.fetchall()
In this example, we retrieve records from the “books” table where the year is greater than 2000.
To order the retrieved data based on specific columns, we can use the ORDER BY clause. This clause allows us to sort the result set in ascending or descending order.
ORDER BY
# Retrieve records and sort them result = connection.execute("SELECT * FROM books ORDER BY year DESC") data = result.fetchall()
In this example, we retrieve records from the “books” table and sort them in descending order based on the “year” column.
To retrieve a specific number of records or skip a certain number of records, we can use the LIMIT and OFFSET clauses.
LIMIT
OFFSET
# Retrieve a limited number of records result = connection.execute("SELECT * FROM books LIMIT 10") data = result.fetchall() # Skip a certain number of records result = connection.execute("SELECT * FROM books LIMIT 10 OFFSET 5") data = result.fetchall()
In the first example, we retrieve the first 10 records from the “books” table. In the second example, we skip the first 5 records and retrieve the next 10 records.
By mastering these techniques, you will be able to insert data into SQLite tables and retrieve specific data using powerful querying capabilities.
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