MySQL questions

In MySQL, JOIN operations are used to combine rows from two or more tables based on related columns. Use `INNER JOIN` to return records with matching values in both tables, `LEFT JOIN` to return all records from the left table and matched records from the right table, and `RIGHT JOIN` for the opposite. For example, `SELECT * FROM orders INNER JOIN customers ON orders.customer_id = customers.id` retrieves orders with customer details.

The `mysqli` (MySQL Improved) extension in PHP provides an interface to interact with MySQL databases. It offers improved functionality over the older `mysql` extension, including support for prepared statements, transactions, and multi-query execution. For example, you can connect to a database with `mysqli_connect('localhost', 'user', 'password', 'database')`. `mysqli` provides both procedural and object-oriented interfaces for database operations.

'mysqli_prepare()' is used in PHP to prepare an SQL statement for execution, allowing for parameterized queries that enhance security. For example: `$stmt = mysqli_prepare($conn, 'SELECT * FROM users WHERE email = ?');`. Placeholders (like `?`) are used in the query, and then parameters are bound using `mysqli_stmt_bind_param()`. This approach helps prevent SQL injection by separating the SQL code from the data.

'mysqli_fetch_assoc()' fetches a result row as an associative array from a MySQL database query. For example: `while ($row = mysqli_fetch_assoc($result)) { echo $row['column_name']; }` retrieves rows from a result set where each row is an associative array with column names as keys. This function is useful for accessing query results in a readable format.

MyISAM is a non-transactional storage engine, ideal for read-heavy applications, while InnoDB supports transactions, foreign keys, and row-level locking, making it suitable for high-concurrency environments. For instance, InnoDB is preferable for e-commerce sites where data integrity is critical.