SQL

mysql check if not null

SELECT * 
FROM table 
WHERE YourColumn IS NOT NULL;

mysql where value is null

SELECT *
FROM contacts
WHERE last_name IS NULL;

if null mysql

SELECT IFNULL(NULL, "W3Schools.com");

mysql if null

IFNULL(MAX(EMAIL), "example@google.com") as email

if column value is null then in mysql

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

check if value is null mysql

SELECT * from TABLE where CODE IS NULL OR CODE!='C'