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Version: 3.1.X

Sorting with PFT

In ABCD and CISIS, sorting is not "dynamic" like in SQL. Instead, you define a Sort Key using a PFT format. The system generates this key for every record and sorts the output based on it.

Key Generation Rules​

  1. Single String: The PFT must produce a single, continuous string.
  2. Fixed Length: For accurate sorting, keys should be padded to a fixed length (e.g., ensure Title always takes 50 chars).
  3. Structure: Primary Key + Secondary Key + Tertiary Key.

Sorting Modes​

Heading Mode (mhl, mhu)​

When generating sort keys, it is best practice to use Heading Mode.

  • Function: It ignores characters enclosed in <...> (non-filing characters).
  • Example: If a title is stored as <The >History of Time:
    • mpu (Proof Mode): Sorts under T ("THE HISTORY...").
    • mhu (Heading Mode): Sorts under H ("HISTORY...").

Common Sort Formats​

1. Simple Alphabetic Sort (Title)​

Sort by Title (Tag 24).

mhu, v24

2. Hierarchical Sort (Author + Date)​

Sort by Author (Tag 70), and for the same author, sort by Date (Tag 26).

Problem: If Author is "Smith" and Date is "2023", simply writing v70 v26 might fail if another record has Author "Smithson" and Date "2021" (Smithson > Smith). Solution: Pad the first field with spaces to a fixed length.

mhu,
/* Author: 60 characters fixed width */
v70, s(v70, x60)*0.60,
/* Date: 4 characters */
v26

3. Numeric Sorting​

CISIS sorts strings alphabetically ("10" < "2"). To sort numbers correctly (2 < 10), you must pad them with zeros using f().

Example: Sorting by Call Number (Tag 50)

/* Format number to 10 digits with leading zeros */
f(val(v50), 10, 0)

Result: 2 becomes 0000000002, which sorts before 0000000010.

4. Descending Order (Inverted Sort)​

CISIS only sorts in ascending order (A-Z, 0-9). To get descending order (e.g., most recent year first), you must mathematically invert the value using the Complement of 9.

Example: Sort by Year (Tag 64) Descending

f(9999 - val(v64), 4, 0)

Logic:

  • Year 2023 -> 9999-2023 = 7976
  • Year 2000 -> 9999-2000 = 7999
  • Since 7976 < 7999, the year 2023 comes first in ascending sort.