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How to use the notnull annotation
The usage is to limit the value range of the field by setting field constraints to avoid data errors or situations that do not comply with business rules. For more information on how to use the notnull annotation, you can read the following article.
How to delete not null restriction in mysqlIn mysql, you can use the "ALTER TABLE" statement to delete the "not null" non-null restriction from the columns of the specified table. You can use modify to modify the data type and constraints of the fields in the table. The syntax is "ALTER TABLE table name MODIFY field name INT NULL;".
How to modify the not null attribute in mysqlMySQL is a very popular relational database management system that allows users to create, modify, and delete tables as well as query and operate data in tables. In MySQL, when we create a table, we can set a property for each column, such as data type, default value, primary key, foreign key, etc. Among them, a common attribute is NOT NULL, which means that the value of this column cannot be empty. In some cases, we may need to modify the NOT NULL attribute of a table. For example, when we create a table, we may not know
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