in 和 exist 区别

https://blog.csdn.net/lick4050312/article/details/4476333?spm=1001.2101.3001.6650.3&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-3-4476333-blog-109291670.pc_relevant_multi_platform_whitelistv3&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-3-4476333-blog-109291670.pc_relevant_multi_platform_whitelistv3&utm_relevant_index=6