自己捣鼓出来了
SELECT
b.*,
c.alipayUserId,
c.min_date
FROM
`al_user` b
LEFT JOIN
(
SELECT
a.`alipayUserId`,
MIN(a.`createDate`) min_date
FROM
`al_orders` a
WHERE 1 = 1
GROUP BY a.`alipayUserId`
) c
ON b.`alipayUserId` = c.alipayUserId
WHERE c.min_date > '2018-04-27 00:00:00'
AND c.min_date < '2018-04-28 23:59:59'