varchar和int mysql数据类型的默认值 [英] Default values for varchar and int mysql data types

问题描述

屏幕截图显示了3种典型的数据类型定义:id(自动递增)，标题和数字.

The screenshot show 3 typical definitions of data type: id (autoincrement), a title and a number.

1.- none和NULL之间有什么区别?
2.-如果我想要一个空字符串，是否必须为varchar类型选择as defined: ''?
3.-是否必须为自动增量类型输入as defined: 0默认值?

1.- Which are differences between: none and NULL?
2.- Do I must choose as defined: '' for varchar types when I want an empty string?
3.- Do I must put an as defined: 0 default value for autoincrement int types?

推荐答案

默认无表示没有默认值.如果插入内容中未提供值，则查询将失败，并显示无默认值错误".

Default none means there is no default value. If a value is not provided on an insert, the query will fail with a "no default value error".

NULL是实际的NULL值，这意味着如果在插入中未提供任何值，则该列将默认为NULL(空).对于varchar，您可以将default设置为''，但是NULL更好.

NULL is the actual NULL value meaning if no value is provided on an insert the column will default to NULL (empty). For varchar you can set default to '', but NULL is better.

Autoincrement int类型不应具有默认值(默认值:无)，因为它将始终具有值.

Autoincrement int types shouldn't have a default value (Default: None) because it will always have a value.

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