Specific process is like this, first create a new table, the following
The CREATE TABLE Persons_Form
(
Id_P int the NOT NULL,
The LastName varchar (255) NOT NULL,
FirstName varchar (255),
Address varchar (255),
City varchar (255) the DEFAULT 'SANDNES')

Then insert the two rows of data, the effect the following



Then through the ALTER TABLE Persons_Form ALTER city DROP DEFAULT statement to city, the corresponding DEFAULT data to withdraw, then the state of the page is





After going to by INSERT INTO Persons_Form (Id_P, LastName) VALUES (3, "Koby") to INSERT the row data, but the system error, shown below, so I want to ask why the City's default is Null, why the system will prompt no default value, are inserting data after all to include the content of City