Post create sql - auto increment?

[Hamder83]

Hi 

I'm using this snippet of code:

ALTER TABLE UB_SalesAgreements
ALTER COLUMN ID bigint NOT NULL;

ALTER TABLE UB_SalesAgreements

ADD PRIMARY KEY (ID);

I want to add AUTO INCREMENT
https://www.w3schools.com/sql/sql_autoincrement.asp

I tried:

ALTER COLUMN ID bigint NOT NULL AUTO INCREMENT;
AND 

ALTER COLUMN ID bigint NOT NULL;

ALTER COLUMN ID bigint AUTO INCREMENT; 

but it does not work?

[Hamder83]

Or like this maybe?

ALTER TABLE UB_SalesAgreements
ALTER COLUMN ID IDENTITY(1,1);