Append a Point to a LineString in MySQL

SET @ls = LineString(Point(0, 0), Point(0, 1));

WITH RECURSIVE 
    nums (n) AS (SELECT 1 UNION ALL SELECT n + 1 FROM nums WHERE n < ST_NumPoints(@ls)), 
    points (p) as (SELECT ST_PointN(@ls, n) FROM nums UNION ALL SELECT Point(2, 3)) 
SELECT CAST(ST_Collect(p) AS LINESTRING) INTO @ls FROM points;

SELECT ST_AsText(@ls);

+-------------------------+
| ST_AsText(@ls)          |
+-------------------------+
| LINESTRING(0 0,0 1,2 3) |
+-------------------------+