Ignoring the indexes and just focusing on the main table sizes reported, we have:

- String ("The frequent repetition of these names inflates the size of the table"): 392 MB

- Enum data type ("Internally, an enum type is stored as four-byte floating point number. So it saves space in the table [...]"): 338 MB

- Lookup table ("Also, since a smallint only occupies two bytes, the person_l table can potentially use less storage space than the other solutions"): 338 MB.

I just can't make sense of the numbers, especially given the authors comments that I've quoted.

Is this some kind of typo/editing fail?

  SELECT person_id
  FROM person_l
  WHERE state_id = (SELECT id FROM state_l WHERE name = 'Burgenland');

separations of types and relations should be limited to core atomic type, string, int , date etc ... (althought date is debatable as is not usually atomic in most cases, and many dbs end up with one more date relations)

anyway, always use a table .. when its a choice

In a lot of web apps this need tends to be related to validation, so many just do these lookups and simple comparisons in their app logic and based on static values from config files long before any db query is made. Sometimes you just don't need to involve the database and the performance would be better for it anyway.