Overview
In this tutorial, we will learn about SQLite NOT NULL constraint. We can specify this constraint to a column during the database table creation.
SQLite NOT NULL Constraint
The SQLite NOT NULL constraint ensures a column cannot have a NULL value. When you define a column with the NOT NULL constraint, it means that every row in the table must have a non-NULL value for that column.
Syntax
The general syntax of the constraint is as follows:
CREATE TABLE table_name (
column1 datatype NOT NULL,
column2 datatype,
…
);
By default, a column can hold NULL values. The NOT NULL constraint enforces a column to NOT accept NULL values. This enforces a column to contain a value, meaning you cannot insert a new record or update a record without adding a value to this column.
Example
Let’s understand the concept with the help of an example. Consider the following CREATE TABLE statement.
CREATE TABLE demo_table (
column1 INTEGER NOT NULL,
column2 TEXT
);
The demo_table has two columns. column1 is NOT NULL, meaning the column cannot contain NULL values.
Insert data into the table using the following INSERT statement:
INSERT INTO demo_table VALUES(1,’ABC’);
INSERT INTO demo_table VALUES(2,’XYZ’);
INSERT INTO demo_table VALUES(3,’ ‘);
INSERT INTO demo_table VALUES(4);
INSERT INTO demo_table VALUES(4, NULL);
INSERT INTO demo_table VALUES(NULL,’PQR’);
Attempting to set the column value to NULL when inserting a new row or updating an existing one causes a constraint violation.SQLite will generate a runtime error if you try to insert or update a row without providing a value for a column with the NOT NULL constraint.
In the following INSERT statement, an error has occurred.
INSERT INTO demo_table VALUES(NULL,’PQR’);
We tried inserting NULL into a column defined with NOT NULL constraint.
An error has occurred, and the insert was not successful. A violation of the NOT NULL constraint has occurred.
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SQLite Tutorials
SQLite tutorials on this website:
https://www.testingdocs.com/sqlite-database-tutorials/
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