mysql分隔字符串查询

SELECT
SUBSTRING_INDEX(a.TimeString, ';', 1) AS c1,
SUBSTRING_INDEX(
SUBSTRING_INDEX(a.TimeString, ';', 2),
';' ,- 1
) AS c2,
SUBSTRING_INDEX(a.TimeString, ';', 2) AS c3
FROM
ras_attresultrecord AS a
LEFT JOIN ras_users AS u ON a.UID = u.UID
WHERE
AttDate BETWEEN "20170201"
AND "20170331"