PostgreSQL新增一列的pl/sql脚本

多次运行不会报错

DO language plpgsql $$BEGIN    RAISE INFO '*************** test_add_column.sql begins'' ***************';    if not exists (select 1 from information_schema.columns where table_schema = 'public'          and table_name = 'qer_simutrade_param'         and column_name = 'pool_id')    thenRAISE INFO '*************** column npool_id not exist, add now... ***************';        alter table public.qer_simutrade_param add column pool_id varchar;    end if;    RAISE INFO '*************** test_add_column.sql completes'' ***************';    EXCEPTION      WHEN OTHERS THEN        RAISE NOTICE '*************** Patch ''test_add_column.sql'' fails : ErrCode (%) (%)', SQLSTATE, SQLERRM;        RAISE;END;$$;