Postgres 12

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CREATE TABLE poi(longitude numeric, latitude numeric);
CREATE TABLE project_options (srid int);
INSERT INTO project_options VALUES (26916);

CREATE TABLE

CREATE TABLE

INSERT 0 1

DO $$
DECLARE
    sridval int;
BEGIN
    sridval := (SELECT srid FROM project_options);	
	EXECUTE FORMAT('ALTER TABLE poi ADD coords geometry(point, %s)',sridval);
END $$;

SELECT * FROM poi; 

DO

longitude
latitude
coords

SELECT 0

DROP TABLE poi;
CREATE TABLE poi(longitude numeric, latitude numeric);

DROP TABLE

CREATE TABLE

DO $$
BEGIN
  EXECUTE FORMAT('ALTER TABLE poi ADD coords geometry(point, %s)',
		 (SELECT srid FROM project_options));
END $$;

SELECT * FROM poi; 

DO

longitude
latitude
coords

SELECT 0

DROP TABLE poi;
CREATE TABLE poi(longitude numeric, latitude numeric);

DROP TABLE

CREATE TABLE

DO $$
BEGIN
  EXECUTE FORMAT('ALTER TABLE poi ADD coords geometry(point, %s) 
                  GENERATED ALWAYS AS (ST_MakePoint(longitude, latitude)) STORED;',
		 (SELECT srid FROM project_options));
END $$;

SELECT * FROM poi; 

DO

longitude
latitude
coords

SELECT 0