ifnull sql code example

Example 1: if column value is null then in mysql

SELECT 
    contactname, IFNULL(bizphone, homephone) phone
FROM
    contacts;

Example 2: mysql select default if null

IFNULL(MAX(EMAIL), "[email protected]") as email

Example 3: if else sql

IF Boolean_expression
BEGIN
    -- Statement block executes when the Boolean expression is TRUE
END
ELSE
BEGIN
    -- Statement block executes when the Boolean expression is FALSE
END

Example 4: 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
);