How to change data type size with query in SQL Server

 If we need to change the data type size of a particular column then we use alter table statement.

“The ALTER TABLE statement is used for add, delete, or modify columns in an existing table.”

Syntax:-

ALTER TABLE tablename

ALTER COLUMN columnname datasize

suppose we have 

we have a login table (login) and that have three columns i.e. user_id username and pwd with some datatype size as below:-

now if we want to change the space nvarchar(50) to nvarchar(max) so we just write the below query and we can get this:-

ALTER TABLE login

ALTER COLUMN username nvarchar(max)