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SQL NOT NULL:
- SQL – NOT NULL is a constraint which is used not to store null values in a column while inserting new records in a table. Always, SQL NOT NULL constraint ensures a column have SQL NOT NULL value.
- If we try to insert/update null values into NOT NULL columns, then, the query will be aborted.
- Syntax for SQL – NOT NULL constraint is given below.
Syntax for SQL – NOT NULL constraint:
| SQL Syntax for NOT NULL constraint | CREATE TABLE table_name (column_name1 data_type(size) NOT NULL, column_name2 data_type(size) NOT NULL, column_name3 data_type(size), etc…); |
Note: If we do not mention NOT NULL constraint, then, a table can hold NULL values by default.
Example for how to use SQL – NOT NULL constraint:
- Please execute below query in SQL to create a table with NOT NULL constraint.
| CREATE TABLE student (Student_ID int NOT NULL, Student_name varchar(255) NOT NULL, City varchar(255), Marks int); |
- Now, a new table called “student” is created and the fields “Student_ID” and “Student_name” are specified as NOT NULL. So, these 2 columns can’t be inserted or updated with NULL values.