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在MySQL中 如下： 首先有个名字为business的表： SELECT ISNULL(business_name,'no business_name') AS bus_isnull FROM business WHERE id=2 直接运行就会报错： 错误代码： 1582 Incorrect parameter count in the call to native function 'isnull' 所以， 使用 SELECT IFNULL(business_name,'no business_name') AS bus_ifnull FROM business WHERE id=2 运行结果：
当查询的值不为null时： SELECT IFNULL(business_name,'no business_name') AS bus_ifnull FROM business WHERE id=1 结果如下：
使用 SELECT COALESCE(business_name,'no business_name') AS bus_coalesce FROM business WHERE id=2 结果如下： 当查询值不为null时： SELECT COALESCE(business_name,'no business_name') AS bus_coalesce FROM business WHERE id=1 其中： SELECT COALESCE(business_name,district_id,id) AS bus_coalesce FROM business WHERE id=2 那么， SELECT * FROM business WHERE ISNULL(business_name) 结果如下：
同样， SELECT * FROM business WHERE business_name IS NULL 结果如下： SELECT * FROM business WHERE business_name IS NOT NULL 总结 以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如有疑问大家可以留言交流，谢谢大家对极客世界的支持。 |
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