Syntax
------

var_name := expr

Description
-----------

Assignment operator for assigning a value. The value on the right is assigned
to the variable on left.

Unlike the = operator, := can always be used to assign a value to a variable.

This operator works with both user-defined variables and local variables.

When assigning the same value to several variables, LAST_VALUE() can be useful.

Examples
--------

SELECT @x := 10;
+----------+
| @x := 10 |
+----------+
|       10 |
+----------+

SELECT @x, @y := @x;
+------+----------+
| @x   | @y := @x |
+------+----------+
|   10 |       10 |
+------+----------+

URL: https://mariadb.com/kb/en/assignment-operator/