mysql 嵌套 case when 的问题

sql 语句如下：

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
			'地推会员'
		ELSE
			'普通会员'
		END
	) type,
	(
		CASE
		WHEN a.uc_flag = 0 THEN
			'未确认'
		WHEN a.uc_flag = 1 THEN
			'有效'
		WHEN a.uc_flag = 2 THEN
			'无效'
		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 '新投递'
			ELSE '暂无' END
		) 
		ELSE
		(
			CASE 
			WHEN b.post_status = 0 
			THEN '已预约面试'
			WHEN b.post_status = 1 
			THEN '面试成功'
			WHEN b.post_status = 2 
			THEN '已拒绝'
			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

查询结果如下：

有没有发现 case when 的最外层的判断没有生效，这是为什么？