MySQL CONNECTION_ID

The CONNECTION_ID function in MySQL is used to retrieve the connection ID (thread ID) for the current client session. Each client session that connects to the MySQL server is assigned a unique connection ID, which can be useful for various administrative and diagnostic purposes.

Syntax

The syntax for the CONNECTION_ID function is quite simple:

CONNECTION_ID()

Example

Let’s consider a simple example to demonstrate the usage of the CONNECTION_ID() function. Suppose you have a MySQL server running, and you want to retrieve the connection ID for the current client session:

-- Query to retrieve the connection ID for the current session
SELECT CONNECTION_ID() AS ConnectionID;

This query will return a result set with a single column named ConnectionID containing the connection ID for the current session.

Practical Use Case

The CONNECTION_ID() function can be particularly useful in scenarios where you need to uniquely identify and track individual connections. For example, you might use it in combination with other queries or log entries to monitor and troubleshoot specific client sessions or connections to your MySQL server.

-- Log information about a specific client session using CONNECTION_ID()
INSERT INTO connection_log (connection_id, log_message, log_timestamp)
VALUES (CONNECTION_ID(), 'User logged in', NOW());

In this example, we’re using the CONNECTION_ID() function to insert a log entry into a hypothetical connection_log table, recording the fact that a user has logged in along with the timestamp and connection ID.

Keep in mind that connection IDs are unique only within the scope of a particular MySQL server instance. If a client disconnects and reconnects, it may be assigned a different connection ID.