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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)
Updated on: 10-Oct-2019
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