mysql中如何统计某字段里某个字符的个数？

SELECT
SUM (
(
LENGTH (TRAIN_NO) - LENGTH (REPLACE(TRAIN_NO, ‘,’, ”))
) + 1
)
FROM
NC_PROBLEM_NOTE
WHERE
PART_NUMBER = # { partNumber }
AND MILES BETWEEN # { mileageDown }
AND # { mileageUp }
AND PROBLEM_RESULT != 2678