Check if a field of table has NOT NULL property set in SQL?

To check if field of a table has NOT NULL property, you can use any of the two syntaxes. The first syntax is as follows −

desc yourTableName;

Following is the second syntax −

select column_name,
   is_nullable
   from information_schema.columns
   where table_schema = ‘yourDatabaseName’
   and table_name = 'yourTableName’;

Let us first see an example and create a table −

mysql> create table DemoTable
(
   StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   StudentName varchar(40),
   StudentAge int NOT NULL,
   IsActiveStudent ENUM('ACTIVE",INACTIVE') NOT NULL,
   StudentCountryName varchar(40)
);
Query OK, 0 rows affected (1.53 sec)

The first syntax is as follows to check if field of table has NOT NULL property set −

mysql> desc DemoTable;

This will produce the following output −

+--------------------+--------------------------+------+-----+---------+----------------+
| Field              | Type                     | Null | Key | Default |          Extra |
+--------------------+--------------------------+------+-----+---------+----------------+
| StudentId          | int(11)                  | NO   | PRI | NULL    | auto_increment |
| StudentName        | varchar(40)              | YES  |     | NULL    |                |
| StudentAge         | int(11)                  | NO   |     | NULL    |                |
| IsActiveStudent    | enum('ACTIVE",INACTIVE') | NO   |     | NULL    |                |
| StudentCountryName | varchar(40)              | YES  |     | NULL    |                |
+--------------------+--------------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

The second syntax is as follows to check if field of table has NOT NULL property set −

mysql> select column_name,
   is_nullable
   from information_schema.columns
   where table_schema = 'web'
   and table_name = 'DemoTable';

This will produce the following output −

+--------------------+-------------+
| COLUMN_NAME        | IS_NULLABLE |
+--------------------+-------------+
| StudentId          | NO          |
| StudentName        | YES         |
| StudentAge         | NO          |
| IsActiveStudent    | NO          |
| StudentCountryName | YES         |
+--------------------+-------------+
5 rows in set (0.00 sec)

AmitDiwan

Published on 10-Oct-2019 15:28:32