In MariaDB, every thread (including each event) has an ID that is unique among the set of currently connected clients. The CONNECTION_ID() function is a built-in function that returns the connection ID (thread ID) for the connection.

Syntax

The syntax goes like this:

CONNECTION_ID()

So, no arguments are required or accepted.

Example

Here’s an example to demonstrate:

SELECT CONNECTION_ID();

Result:

+-----------------+
| CONNECTION_ID() |
+-----------------+
|               6 |
+-----------------+

In my case, the connection ID is 6.

If I connect to MariaDB from a new terminal window:

mariadb

And run the statement again:

SELECT CONNECTION_ID();

Here’s what I get:

+-----------------+
| CONNECTION_ID() |
+-----------------+
|               7 |
+-----------------+

No Arguments are Accepted

Passing any arguments to CONNECTION_ID() results in an error:

SELECT CONNECTION_ID(1);

Result:

ERROR 1582 (42000): Incorrect parameter count in the call to native function 'CONNECTION_ID'