SQL - Converting 24-hour (“military”) time (2145) to “AM/PM time” (9:45 pm)

Question

I have 2 fields I\'m working with that are stored as smallint military structured times.
Edit I\'m running on IBM Informix Dynamic Server Version 10.00.FC9

Answer 1

Here's a non-tested port of Steve Kass's solution to Informix.

Steve's solution itself is well tested under MS SQL Server. I like it better than my previous solutions because the conversion to am/pm time is exclusively done algebraically not requiring the help of any branching (with CASE statements and such).

Substitute the @milTime with column name if the numeric "military time" comes from the database. The @ variable is only there for test.

--declare @milTime int
--set @milTime = 1359
SELECT
  CAST(MOD((@milTime /100 + 11), 12) + 1 AS VARCHAR(2))
  ||':'
  ||SUBSTRING(CAST((@milTime%100 + 100) AS CHAR(3)) FROM 2 FOR 2)
  ||' '
  || SUBSTRING('ap' FROM (MOD(@milTime / 1200, 2) + 1) FOR 1)
  || 'm';

For reference here's my [fixed], CASE-based, solution for SQL Server

SELECT 
  CASE ((@milTime / 100) % 12)
      WHEN 0 THEN '12'
      ELSE CAST((@milTime % 1200) / 100 AS varchar(2))
  END 
  + ':' + RIGHT('0' + CAST((@milTime % 100) AS varchar(2)), 2)
  + CASE (@milTime / 1200) WHEN 0 THEN ' am' ELSE ' pm' END