mysql——null值和空值

参考：https://blog.csdn.net/xp178171640/article/details/103065271?spm=1001.2101.3001.6650.2&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-2-103065271-blog-107128984.235%5Ev27%5Epc_relevant_3mothn_strategy_and_data_recovery&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-2-103065271-blog-107128984.235%5Ev27%5Epc_relevant_3mothn_strategy_and_data_recovery&utm_relevant_index=5

 

1、null值只能用 is null查询出来，用in或者=''，用in或者=' ',只能查询到空值

 

 2、占用空间的区别