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    For example,

                       CREATE TABLE Students
                       (
                       StudentID INTEGER, FirstName CHAR(30), LastName CHAR(30) NULL, Marks INT

                       );
                  Now, the LastName field can accept NULL values.

                  NOT NULL Constraint

                  The NOT NULL constraint specifies that a column cannot accept NULL values. You cannot insert a
                  new record, or update a record without specifying a value to this column. For example,

                       CREATE TABLE Students
                       (
                       StudentID INTEGER NOT NULL, FirstName CHAR(30), LastName CHAR(30), Marks INT
                       );

                  Now, the StudentID column cannot accept NULL values.

                  Primary Key Constraint

                  Each record in a table is uniquely identified by the PRIMARY KEY constraint. Primary key must have
                  unique values and can not contains NULL values. A table can only have one primary key, which can
                  be composed of single or multiple columns (fields). For example, Here, the value of the StudentID
                  column is a unique identifier for a row. Similarly, it cannot store NULL value and must be UNIQUE.

                       CREATE TABLE Students
                       (
                       StudentID INTEGER PRIMARY KEY, FirstName CHAR(30), LastName CHAR(30), Marks
                       INT
                       );

                  Foreign Key Constraint

                  The FOREIGN KEY constraint is used to establish a relationship between two tables. It ensures that
                  the value in the referencing table column matches a value in the referenced table’s primary key
                  column. The referenced table is the one that has the main or original data, and the referencing table
                  is the one that uses this data.

                  For example, the following SQL command creates a Courses table where StudentID is a foreign key
                  referencing the Students table:
                       CREATE TABLE Students
                       (
                            StudentID  INTEGER  PRIMARY  KEY,  FirstName  CHAR(30),  LastName  CHAR(30),
                            Marks INT

                       );
                       CREATE TABLE Courses
                       (

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