How to change data-types in sql?

Question

how to change data-types in sql?
i want to change 10 into 15.
how will be my statement?

for example:
username varchar(10)

returns:
username varchar(15)

Answer 1

alter table tablename alter column username varchar(15) not null

Answer 2

You can change it in your db

Answer 3

Hai

Answer 4

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