mysql 嵌套 case when 的問題？

sql語句如下：

SELECT
    a.uc_id id,
    (
        CASE WHEN a.uc_realname IS NULL OR a.uc_realname =''
        THEN a.uc_sys_name ELSE a.uc_realname END
    ) AS realName,
    a.uc_register_time registerTime,
    a.uc_phone phone,
    a.uc_last_login_time lastLoginTime,
    (
        CASE
        WHEN LEFT (a.uc_code, 2) = '00' THEN
            '地推會員'
        ELSE
            '普通會員'
        END
    ) type,
    (
        CASE
        WHEN a.uc_flag = 0 THEN
            '未確認'
        WHEN a.uc_flag = 1 THEN
            '有效'
        WHEN a.uc_flag = 2 THEN
            '無效'
        END
    ) flagName,
    b.post_status,
    (
        CASE 
        WHEN b.post_status IS NULL OR b.post_status = '' 
        THEN 
        (
            CASE
            WHEN tmp.ctime IS NOT NULL AND tmp.ctime <> ''
            THEN '新投遞'
            ELSE '暫無' END
        ) 
        ELSE
        (
            CASE 
            WHEN b.post_status = 0 
            THEN '已預(yù)約面試'
            WHEN b.post_status = 1 
            THEN '面試成功'
            WHEN b.post_status = 2 
            THEN '已拒絕'
            WHEN b.post_status = 3 
            THEN '已失效'
            ELSE '未知' END
        )
        END
    ) `status`,
    tmp.ctime,
    b.memo,
    c.realname manageRealName,
    c.id manageUseId
FROM
    bco_uc.uc_app_user a
LEFT JOIN bco_web.web_crm_dz b ON a.uc_id = b.app_user_id
LEFT JOIN bco_web.web_manage_user c ON b.manage_user_id=c.id
LEFT JOIN (
    SELECT
        t.uc_id,
        MAX(t1.create_time) ctime
    FROM
        bco_uc.uc_app_user t
    LEFT JOIN bco_jobpost.job_position_apply t1 ON t.uc_id = t1.user_id COLLATE utf8mb4_unicode_ci
    WHERE t1.status='draft' GROUP BY t.uc_id
) tmp ON a.uc_id = tmp.uc_id

查詢結(jié)果如下：

有沒有發(fā)現(xiàn)case when的最外層的判斷沒有生效，這是為什么？