migrations.sql

-- BASE DB 
CREATE TABLE IF NOT EXISTS "db_ver" (
    version         integer unique not null,
    updated         timestamp WITH time zone DEFAULT now()
);

INSERT INTO db_ver (version) VALUES (1);  -- init version 1


-- Migrations are named 1.sql, 2.sql etc.

DO $migration$
    DECLARE 
        from_version int;
        to_version int;
    BEGIN 
        from_version := 1;  -- declare the version being migrated from
        to_version  := 2;   -- declare the version being migrated to

        IF (SELECT MAX(version) from db_ver) = from_version THEN

            -- MIGRATION CODE BEGINS

            -- stuff goes here! 

            -- MIGRATION CODE ENDS

            -- UPDATE DB VERSION
            INSERT INTO db_ver (version) VALUES (to_version);

        END IF;
END $migration$;

for FILE in ls ./migrations/* | sort -g; do psql ..... ; done