By default, a table column can hold NULL values. SQL NOT NULL Constraint The NOT NULL constraint enforces a column to NOT accept NULL value...
By default, a table column can hold NULL values.
SQL NOT NULL Constraint
The NOT NULL constraint enforces a column to NOT accept NULL values.The NOT NULL constraint enforces a field to always contain a value. This means that you cannot insert a new record, or update a record without adding a value to this field.
The following SQL enforces the "P_Id" column and the "LastName" column to not accept NULL values:
CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255) ) |
