MySQL:NULL 与“"
对于 MySQL 中的文本字段，使用 default null 还是 default "" 更好?
Is it better to use default null or default "" for text fields in MySQL?
为什么?
更新:我知道每个人的意思.考虑到磁盘空间和性能，我对什么更好用很感兴趣.
Update: I know what means each of them. I am interested what is better to use considering disk space and performance.
更新 2:嘿，伙计们！问题是什么更好用"而不是每个是什么意思"或如何检查它们"......
Update 2: Hey ppl! The question was "what is better to use" not "what each means" or "how to check them"...
推荐答案
使用默认的 null.在 SQL 中，null 与空字符串 ("") 非常不同.空字符串具体表示该值被设置为空；null 表示该值未设置，或设置为空.不同的意思，你看.
Use default null. In SQL, null is very different from the empty string (""). The empty string specifically means that the value was set to be empty; null means that the value was not set, or was set to null. Different meanings, you see.
不同的含义和不同的用法是为什么适当使用它们很重要的原因；使用 default null 而不是 default "" 可能节省的空间量非常小，几乎可以忽略不计；然而，按照惯例使用适当的默认值的潜在价值是相当高的.
The different meanings and their different usages are why it's important to use each of them as appropriate; the amount of space potentially saved by using default null as opposed to default "" is so small that it approaches negligibility; however, the potential value of using the proper defaults as convention dictates is quite high.
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