根据IN子句设置为布尔值

你可以用 CASE .. WHEN

UPDATE clients 
SET online = CASE WHEN id IN(4,5,8,10,12)
                    THEN 1 
                  ELSE 0 
             END
WHERE
    id BETWEEN 2 AND 15 AND parentId = 123;

IN(..) 是逻辑/比较函数。所以你可以做以下事情( )以及:

UPDATE clients 
    SET online = (id IN(4,5,8,10,12)) 
    WHERE
        id BETWEEN 2 AND 15 AND parentId = 123;