Executing SQL queries and retrieving data from databases Mocktest

The UPDATE operation in SQL is used to modify existing data in a database table. It changes the values of specified columns in existing rows based on specified conditions.

The mysqli_num_rows() function in PHP is used to get the number of rows in a result set returned by a SELECT query. It returns the number of rows or false if the query does not return a result set.

The mysqli_query() function in PHP MySQLi extension is used to execute an SQL query. It sends an SQL query to the MySQL database and returns a result object for SELECT queries or a boolean value for other types of queries.

The PDO::exec() method in PHP PDO extension is primarily used for executing an SQL query that does not return a result set, such as INSERT, UPDATE, DELETE, or CREATE statements.

The SQL SELECT operation is used to retrieve data from a database table. It returns a result set containing rows that match the specified conditions or criteria.

The mysqli_fetch_object() function in PHP is primarily used for fetching a row from a result set returned by a SELECT query. It returns an object representing the fetched row's column values, where the object properties are the column names.

The TRUNCATE operation in SQL is used to remove all data from a database table by deleting all rows. Unlike the DELETE operation, which removes specific rows, TRUNCATE removes all rows from the table.

One of the primary advantages of using PDO extension over MySQLi for executing SQL queries in PHP is improved security against SQL injection attacks. PDO provides parameterized queries and prepared statements by default, helping prevent SQL injection vulnerabilities.

The mysqli_affected_rows() function in PHP MySQLi extension is used to get the number of rows affected by an SQL query such as INSERT, UPDATE, DELETE, or REPLACE. It returns the number of affected rows or -1 if the last query did not affect any rows.

The mysqli_close() function in PHP is used to close a previously opened database connection. It releases the resources associated with the connection and frees up memory, helping improve the performance of the PHP application.