Sql not null

This article is tagged with: Sql not null and mysql

how to check if a column is null in sql

SELECT column_name FROM table_name
WHERE column_name IS NULL;

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
);

sql not null

SELECT column_name FROM table_name
WHERE column_name IS NOT NULL;

alter table not null constraint

ALTER TABLE Persons
MODIFY Age int NOT NULL;

Select without null values sql

SELECT column_names
FROM table_name
WHERE column_name IS NOT NULL;

This article is tagged with: Sql not null and mysql