分页的一个问题

这是一次查询
SELECT DISTINCT
( sj_mobile.id ) AS id,
`sj_mobile`.`name`,
`sj_mobile`.`mobile_brand_id`,
`sj_mobile`.`sort`,
`sj_mobile`.`image` 
FROM
`sj_mobile` 
WHERE
`sj_mobile`.`delete_time` IS NULL 
ORDER BY
`sj_mobile`.`sort` DESC
LIMIT 10 OFFSET 30Copy

这也是一次查询
SELECT DISTINCT
( sj_mobile.id ) AS id,
`sj_mobile`.`name`,
`sj_mobile`.`mobile_brand_id`,
`sj_mobile`.`sort`,
`sj_mobile`.`image` 
FROM
`sj_mobile` 
WHERE
`sj_mobile`.`delete_time` IS NULL 
ORDER BY
`sj_mobile`.`sort` DESC
LIMIT 10 OFFSET 20Copy