I want a update query for update mysql database record.

I want a single update query where I want to update email id in database.
In database already contain some email id like :
Id : Email id
1 :
2 :
3 :

if I update id no 1 record and not change this email id and as it is update then not showing already exist like :
1 :
and i update same email id then not showing already exist but here
update on id no 1 then showing already exist and if update
on id no 1 then update this record.

I want a single query no any php condition
like that below insert query :
INSERT INTO tbo_user (User_ID, User_Name, User_Email, Password, Created) SELECT * FROM (SELECT 'anu_12345', 'Anshu Singh', '', '8626fe7dcd8d412a80d0b3f0e36afd4a', '1520835353') AS tmp WHERE NOT EXISTS ( SELECT * FROM tbo_user WHERE User_ID = 'sdfas' or User_Email = '' ) LIMIT 1;