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/