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Read Operations | CRUD
SQL in Python Projects

Read OperationsRead Operations

Read operations in SQLite involve retrieving data from a database table. These operations allow you to fetch and query data stored in your database. Let's explore how you can perform read operations in SQLite:

Basic Read Operation

The most common way to read data from a SQLite database is by using the SQL SELECT statement. Here's a basic example:

In this example, we:

  • Connect to the database;
  • Create a cursor to execute SQL queries;
  • Use a SELECT query to retrieve all records from the "articles" table;
  • Execute the query and fetch all selected records using cursor.fetchall();
  • Iterate through the retrieved data and print it;
  • Finally, close the database connection.

Requests with conditions

Filtering Data

You can also filter data based on specific criteria using the WHERE clause in your SELECT query. For instance:

This query will retrieve records only where the author matches 'John Doe'.

Retrieving Specific Columns

To retrieve specific columns instead of all columns, you can specify the column names in the SELECT statement:

This query will retrieve only the "title" and "author" columns for all records in the "articles" table.

Limiting the Number of Results

You can limit the number of results with the LIMIT clause. For example, to retrieve the first three records:

These are the basic concepts for performing read operations in SQLite. You can customize your SELECT queries to retrieve specific data from your database as needed.

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SQL in Python Projects

Read OperationsRead Operations

Read operations in SQLite involve retrieving data from a database table. These operations allow you to fetch and query data stored in your database. Let's explore how you can perform read operations in SQLite:

Basic Read Operation

The most common way to read data from a SQLite database is by using the SQL SELECT statement. Here's a basic example:

In this example, we:

  • Connect to the database;
  • Create a cursor to execute SQL queries;
  • Use a SELECT query to retrieve all records from the "articles" table;
  • Execute the query and fetch all selected records using cursor.fetchall();
  • Iterate through the retrieved data and print it;
  • Finally, close the database connection.

Requests with conditions

Filtering Data

You can also filter data based on specific criteria using the WHERE clause in your SELECT query. For instance:

This query will retrieve records only where the author matches 'John Doe'.

Retrieving Specific Columns

To retrieve specific columns instead of all columns, you can specify the column names in the SELECT statement:

This query will retrieve only the "title" and "author" columns for all records in the "articles" table.

Limiting the Number of Results

You can limit the number of results with the LIMIT clause. For example, to retrieve the first three records:

These are the basic concepts for performing read operations in SQLite. You can customize your SELECT queries to retrieve specific data from your database as needed.

Все було зрозуміло?

Секція 3. Розділ 4
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