mysql的case when字段为空,null的问题

mysql的case when字段为空,null

name字段为null时替换为 ‘该字段为空’

SELECT 
CASE 
WHEN name is null THEN '该字段为空'
ELSE name
END as name
,email_id
 FROM mysql_table_name

case when 判断null（已测试）

SELECT
		(case when cdi.DEVICE_TAG is not null then cdi.DEVICE_TAG else '暂无数据' end) as deviceTag,
		(case when cdi.DEVICE_CODE is not null then cdi.DEVICE_CODE else '暂无数据' end) as deviceCode,
		(case when sc.full_name is not null then sc.full_name else '暂无数据' end) as deviceVendor,
		(case when ct.CLASS_NAME is not null then ct.CLASS_NAME else '暂无数据' end) as deviceTypeNameB,
		(case when cdi.DEVICE_PORT is not null then cdi.DEVICE_PORT else '暂无数据' end) as devicePort,
		(case when cdi.CREATE_TIME is not null then cdi.CREATE_TIME else '暂无数据' end) as createTimeStr
-- 			cdi.DEVICE_TAG as deviceTag,
-- 			cdi.DEVICE_CODE as deviceCode,
-- 			sc.full_name as deviceVendor,
-- 			ct.CLASS_NAME as deviceTypeNameB,
-- 			cdi.DEVICE_PORT as devicePort,
-- 			cdi.CREATE_TIME as createTimeStr
		FROM
			con_device_info AS cdi
		LEFT JOIN sys_code AS sc ON sc.code_value = cdi.DEVICE_VENDOR
		LEFT join con_type as ct on ct.ID=cdi.DEVICE_TYPE
		where cdi.ID=#{id}

重点：

case when xxx

is null 或者is not null