NOT NULL constraints:
The NOT NULL constraints restricts null value in database table.
Syntax:
CREATE TABLE Employee(id int, emp_name nvarchar(18) NOT NULL);
This statement create table employee, in that emp_name should not be null value.
DESC Employee
Desc statement describe the table.
Field | Data Type | Null | key | Default |
id | INT | NO | ||
emp_name | NVARCHAR(18) | NO |
CREATE TABLE Course(id int NOT NULL, Course_name nvarchar(20));
Desc Course (in Oracle)
Field | Data Type | Null | key | Default |
id | INT | NO | ||
Course_name | NVARCHAR(20) | NO |
Using Alter to Set NOT NULL:
ALTER TABLE course ALTER COLUMN Course_name nvarchar(20) NOT NULL; in MSSQL server.
ALTER TABLE Course MODIFY Course_name nvarchar(20) NOT NULL; in ORACLE.
ALTER TABLE Course MODIFY COLUMN Course_name nvarchar(20) NOT NULL; in MSACCESS.
Desc Course.
Field | Data Type | Null | key | Default |
id | INT | NO | ||
Course_name | NVARCHAR(20) | NO | |
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