Question

I have a table:

create table A (
    KEY VARCHAR(1024) not null
);

where KEY is primary key. Now I want to create another autoincrement column ID BIGINT, drop exiting primary key constraint and make created column ID as primary key.

How to do this without loosing my data?

Sure I can use temporary table, but try to find right way.

Answer 1

ALTER TABLE A DROP PRIMARY KEY;

ALTER TABLE A ADD COLUMN ID BIGINT NOT NULL WITH DEFAULT 0;

ALTER TABLE A ALTER COLUMN ID SET GENERATED ALWAYS AS IDENTITY(START WITH 1, INCREMENT BY 1);

REORG TABLE A;

UPDATE TABLE A SET ID = DEFAULT;

ALTER TABLE A ADD PRIMARY KEY (ID);