commissioner 表如下：
arrangement 表如下：
现有sql语句如下：
DROP TABLE IF EXISTS temp_arrangement;
CREATE TABLE temp_arrangement
SELECT
`arrangement`.`id`,
`arrangement`.`projectid`,
`arrangement`.`courseid`,
`arrangement_date`.`date` AS `traindate`,
GROUP_CONCAT(`arrangement`.`teacherid` ORDER BY `arrangement`.`teacherid` ASC) AS `teacherids`,
`arrangement`.`commissionerids` AS `commissionerids`,
GROUP_CONCAT(DISTINCT `commissioner`.`name` ORDER BY `commissioner`.`id` ASC) AS `commissionernames`,
`arrangement`.`time`,
`arrangement`.`traindays`,
SUM(CASE WHEN `arrangement`.`traindays`=0 THEN `arrangement`.`time` ELSE `arrangement`.`traindays` END) AS `usetime`
FROM
`arrangement`
INNER JOIN
`arrangement_date`
ON
DATE(`arrangement_date`.`date`) BETWEEN DATE(`arrangement`.`startdate`) AND DATE(`arrangement`.`enddate`)
LEFT JOIN
`commissioner`
ON FIND_IN_SET(`commissioner`.`id`,`arrangement`.`commissionerids`)
WHERE DATE( `arrangement_date`.`date`) BETWEEN DATE(""2015-07-01"") AND DATE(""2015-07-10"")
GROUP BY `arrangement`.`projectid`,`arrangement`.`courseid`, `arrangement_date`.`date` ;
SELECT a.* FROM temp_arrangement AS a ORDER BY
(SELECT MIN(b.traindate) FROM temp_arrangement AS b WHERE projectid=a.projectid),a.projectid,a.traindate;
执行结果如下图所示：
想实现GROUP_CONCAT(“”`arrangement`.`teacherid`””)之后的teacherids不重复，且usetime应该以teacherids的个数为根据来进行求和，即：teacherids去重复后，如果teacherids为单个数字，没有逗号分隔，则usetime对应的应该是1，而不是上图中的2。
当然，GROUP_CONCAT(DISTINCT `arrangement`.`teacherid`)可以去重复，但usetime却不是想要 的效果。
想请教各位达人，要实现下图这种效果，要怎么改进sql语句呢？
