CTE to match days after discharge and days supply from prescription

I'm assuming CTE is the most efficient way to do this, but any suggestions would be great. I think I can do this in multiple steps a different way if I have to, but would love to make this as efficient as possible since the table is huge. I have a table like this:

I need to produce a table which keeps one line per patient discharge and creates 30 new columns indicating whether or not the patient had an antibiotic that day, like this:

However, for the purposes of this post, I'll certainly settle for a solution that produces the following and then I can transpose it. Note - I am only keeping the records in which a patient started a prescription within 1-30 days post discharge. So you'll notice I left out patient #3 below.

Any suggestions are greatly appreciated. Thank you!

For the first option, the best way (if not very concise) is to just use a bunch of CASE expressions.

SELECT
  p.PatientID,
  p.DischargeDate,
  p.RxDate,
  p.DaysSupply,
  CASE WHEN p.DaysSupply >= 01 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day01,
  CASE WHEN p.DaysSupply >= 02 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day02,
  CASE WHEN p.DaysSupply >= 03 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day03,
  CASE WHEN p.DaysSupply >= 04 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day04,
  CASE WHEN p.DaysSupply >= 05 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day05,
  CASE WHEN p.DaysSupply >= 06 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day06,
  CASE WHEN p.DaysSupply >= 07 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day07,
  CASE WHEN p.DaysSupply >= 08 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day08,
  CASE WHEN p.DaysSupply >= 09 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day09,
  CASE WHEN p.DaysSupply >= 10 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day10,
  CASE WHEN p.DaysSupply >= 11 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day11,
  CASE WHEN p.DaysSupply >= 12 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day12,
  CASE WHEN p.DaysSupply >= 13 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day13,
  CASE WHEN p.DaysSupply >= 14 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day14,
  CASE WHEN p.DaysSupply >= 15 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day15,
  CASE WHEN p.DaysSupply >= 16 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day16,
  CASE WHEN p.DaysSupply >= 17 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day17,
  CASE WHEN p.DaysSupply >= 18 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day18,
  CASE WHEN p.DaysSupply >= 19 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day19,
  CASE WHEN p.DaysSupply >= 20 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day20,
  CASE WHEN p.DaysSupply >= 21 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day21,
  CASE WHEN p.DaysSupply >= 22 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day22,
  CASE WHEN p.DaysSupply >= 23 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day23,
  CASE WHEN p.DaysSupply >= 24 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day24,
  CASE WHEN p.DaysSupply >= 25 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day25,
  CASE WHEN p.DaysSupply >= 26 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day26,
  CASE WHEN p.DaysSupply >= 27 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day27,
  CASE WHEN p.DaysSupply >= 28 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day28,
  CASE WHEN p.DaysSupply >= 29 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day29,
  CASE WHEN p.DaysSupply >= 30 THEN CAST(1 AS bit) ELSE CAST(0 AS bit) END AS Day30
FROM Patient p
WHERE DATEADD(day, 30, p.DischargeDate) > p.RxDate;

For the second option you can use GENERATE_SERIES to dynamically generate more rows, and some date math.

SELECT
  p.PatientID,
  p.DischargeDate,
  DATEADD(day, g.value, p.RxDate) AS RxDate
FROM Patient p
CROSS APPLY GENERATE_SERIES(0, p.DaysSupply - 1) g
WHERE DATEADD(day, 30, p.DischargeDate) > p.RxDate;

db<>fiddle