IS NOT NULL code example

Example 1: javascript not null

if (variable !== null) {
  console.log("Var is NOT null");
}

Example 2: javascript is not null

if(data !== null && data !== '') {
   // do something
}

Example 3: sql not null

SELECT column_name FROM table_name 
WHERE column_name IS NOT NULL;

Example 4: Select without null values sql

SELECT column_names
FROM table_name
WHERE column_name IS NOT NULL;

Example 5: how to check if a column is null in sql

SELECT column_name FROM table_name 
WHERE column_name IS NULL;

Example 6: NOT NULL SQL

By default, a column can hold NULL values.
The NOT NULL constraint enforces a column to NOT accept NULL values.
This enforces a field to always contain a value, which means that you cannot insert a new record, or update a record without adding a value to this field.

Sql NOT NULL in creating a table
CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255) NOT NULL,
    Age int
);