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’

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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）

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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

总结

以上为个人经验，希望能给大家一个参考，也希望大家多多支持服务器之家。

原文链接：https://blog.csdn.net/weixin_40277264/article/details/108664454