--         File: type_safety_2.sql
--      Version: 1.1
-- Last Changed: 2017-02-09
--           by: Damir;  https://www.damirsystems.com
--      Project: Types and Typos in SQL
--  Description: Part 2
--           DB: PostgreSQL

CREATE TYPE currency AS ENUM
    ('USD', 'CAD', 'EUR', 'GBP');

-- CUR as text
CREATE TABLE T1 (
      TX  integer        NOT NULL
    , AMT decimal(19,2)  NOT NULL
    , CUR char(3)        NOT NULL -- <--  focus here

    , CONSTRAINT pk_T1 PRIMARY KEY (TX)
);

-- CUR as enum
CREATE TABLE T2 (
      TX  integer       NOT NULL
    , AMT decimal(19,2) NOT NULL
    , CUR currency      NOT NULL -- <-- focus here

    , CONSTRAINT pk_T2 PRIMARY KEY (TX)
);

-- Same data for both tables
--
INSERT INTO T1
    VALUES (1, 10.0, 'USD')
         , (2, 13.0, 'CAD')
         , (3,  9.0, 'EUR') ;

INSERT INTO T2 (TX, AMT, CUR)
        SELECT  TX, AMT, CUR::currency
        FROM T1 ;