Explain NOT NULL constraint ?

The NOT NULL constraint allows a column not to accept NULL values. This specify that NOT NULL Constraint enforce the field to accept a value. Simply, neither you insert or update a new record without  adding a value to this field.

 

Syntax:

 

CREATE TABLE table_name

(

 column1 datatype NOT NULL,

 column1 datatype NULL/NOT NULL,

 column1 datatype

);