CREATE TABLE Polygons (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50),
    polygon MULTIPOLYGON
);

INSERT INTO Polygons (name, polygon) VALUES 
('Polygon 1', 
    MULTIPOLYGON(
        ((0 0,0 5,5 5,5 0,0 0)),
        ((2 2,3 2,3 3,2 3,2 2))
    )
),
('Polygon 2', 
    MULTIPOLYGON(
        ((4 4,4 7,7 7,7 4,4 4)),
        ((5 5,6 5,6 6,5 6,5 5))
    )
);

CREATE TABLE Points (
    id INT AUTO_INCREMENT PRIMARY KEY,
    point POINT
);

INSERT INTO Points (point) VALUES 
(POINT(1,1)),
(POINT(2,2)),
(POINT(3,3)),
(POINT(4,4)),
(POINT(5,5)),
(POINT(6,6)),
(POINT(7,7)),
(POINT(8,8)),
(POINT(9,9));

SELECT * FROM Points WHERE ST_WITHIN(point,(
    SELECT polygon FROM Polygons WHERE name='Polygon 1'
));

+----+-----------+
| id |   point   |
+----+-----------+
|  2 | POINT(2,2)|
|  3 | POINT(3,3)|
+----+-----------+

SELECT *
FROM Points
INNER JOIN Polygons
ON ST_WITHIN(point,polygon);