【MySQL】Invalid use of NULL value

1. Tool: Navicat
2. Database: MySQL
3. Situation mirror: "Add a field" to a certain table. When adding the field "type" initially, "is not null" is not checked, as shown in Figure 1 below. Due to requirements, this field needs to be checked "not null". If you check directly on the basis of Figure 1, an error will be reported, as shown in Figure 2 below.
   
   
4. Solution
   删除该字段，重新设置