How to add an identity column to an existing table

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Let’s say your existing table is Test and it has two columns (X and Y).
You need a third column which will be an identity column and it will be named as ID

 

CREATE TABLE Test1 like Test;

ALTER TABLE Test1 add column ID integer not null;

ALTER TABLE Test1 alter column ID set generated always as identity;

INSERT INTO Test1 (X,Y) SELECT X,Y FROM Test;

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