In SQLite, the
NOT NULL operator is used to filter data in a
SELECT statement based on the presence or absence of a value in a specific column. When used in a
SELECT statement, the
NOT NULL operator returns only those rows where the specified column has a non-null value.
Here’s the basic syntax for using the
NOT NULL operator in a SELECT statement:
SELECT column1, column2, ... FROM table_name WHERE column_name IS NOT NULL;
In this syntax, “column_name” is the name of the column for which you want to check the null value. When you use the
IS NOT NULL operator, SQLite will return only those rows where the specified column has a non-null value.
For example, let’s assume that you have a table named “customers” with the following columns: “customer_id”, “first_name”, “last_name”, and “email_address”. If you want to retrieve all rows where the email_address column has a non-null value, you can use the following SELECT statement:
SELECT customer_id, first_name, last_name FROM customers WHERE email_address IS NOT NULL;
This statement will return only those rows where the email_address column has a non-null value. Any rows with a null value in the email_address column will be excluded from the result set.
In conclusion, the
NOT NULL operator in a
SELECT statement is a useful tool for filtering data based on the presence or absence of a value in a specific column. It can help you retrieve only the data you need and exclude any rows that don’t meet your criteria.