This SQL query creates a computed column (`Lsa_Used`) by performing...

This SQL query creates a computed column (Lsa_Used) by performing several arithmetic and string formatting operations. The code combines mathematical calculations, a subquery, and string formatting functions. Below are the specific steps it executes:

Step-by-Step Explanation:

1. Obtains a Value from the revfac Table:

   • There is a subquery inside a larger computation:

     (select x.revfac
      from revfac x,
           (select max(a.yoe) as MAX_YOE, a.factype
              from revfac a
             where a.factype = 'LTAA'
             group by a.factype) y
      where x.factype = y.factype
        and x.yoe = y.MAX_YOE)
     

     • This subquery fetches the revfac value (x.revfac) from the revfac table (x) where:
       • factype is 'LTAA'.
       • yoe corresponds to the maximum yoe (y.MAX_YOE) for that factype ('LTAA').

   • Effectively, this retrieves the revfac value for the record with the latest yoe (Year of Experience) for the factype 'LTAA'.

2. Performs Arithmetic Operations: The value fetched in step 1 is combined with the column l.PERCENT_LTA_USED to compute a result using the following formula:

   round(((l.PERCENT_LTA_USED / 400) * fetched_revfac_value), nvl(l.PERCENT_LTA_USED, 0))
   

   Explanation:

   • l.PERCENT_LTA_USED / 400: Divides the PERCENT_LTA_USED value (from table l) by 400.
   • * fetched_revfac_value: Multiplies the result by the revfac value fetched from the subquery.
   • nvl(l.PERCENT_LTA_USED, 0): If l.PERCENT_LTA_USED is null, it uses 0.
   • round(..., 2): Rounds the entire calculation to 2 decimal places.

3. Formats the Result as a String:

   TO_CHAR(..., 'fm99G999G999G999G999D00')
   

   • This converts the numeric result from step 2 into a formatted string using the TO_CHAR function.
   • The format mask 'fm99G999G999G999G999D00' applies these specific formatting rules:
     • fm: Suppresses leading spaces for the number.
     • 99G999: Adds separators (e.g., commas ,) for groups of thousands.
     • D00: Ensures 2 decimal places and formats the decimal part.

4. Aliases the Result as Lsa_Used:

   • The entire expression is aliased as Lsa_Used, which can be used as a column in the output.

Overall Purpose:

This code calculates a derived column (Lsa_Used) based on:

• A percentage value (l.PERCENT_LTA_USED),
• A revfac value from the revfac table (specifically for the maximum yoe associated with the factype 'LTAA'),
• Arithmetic operations, and
• String formatting for the final output.

The resulting column (Lsa_Used) is a human-readable formatted string representing the computed value.