SQL統計某分隔符數量

SELECT (
    CASE WHEN p.c_dept_id = '' OR p.c_dept_id IS NULL 
    THEN 0 
    ELSE (LEN(p.c_dept_id) - LEN(REPLACE(p.c_dept_id,',','')))+1
    END) AS c_xf_dept_count,
    p.* 
FROM [t_Public_Opinion] AS p