# 17-matching-2stage-N-1: Two-Stage N:1 Matching

## 电信业务场景

线路→请求书二级汇集。两段式N:1汇集。第一段:多条线路CDR→中间汇总；第二段:中间汇总→请求书。

## Description

Two-stage N:1 matching process. Stage 1 performs N:1 matching from multiple
master records through detail records to an intermediate file. Stage 2 performs
another N:1 match from the intermediate file to a final reference file.

This tests the ability to chain N:1 matching operations across two stages,
where the intermediate result of one N:1 match feeds into a second N:1
match. The final output contains only records that successfully matched
in both stages.

## Record Layout

Standard record (45 bytes, copybook STD-REC.cpy):
| Field      | Type              | Length | Description        |
|------------|-------------------|--------|--------------------|
| STD-KEY    | PIC X             | 10     | Record key         |
| STD-DATA-1 | PIC X             | 20     | Text data          |
| STD-DATA-2 | PIC 9             | 10     | Numeric data       |
| STD-DATA-3 | PIC S9(7)V99 COMP-3| 5    | Packed decimal     |

## Files

| File                               | Purpose                              |
|------------------------------------|--------------------------------------|
| main-17-matching-2stage-N-1.cbl    | Main COBOL program (fixed format)    |
| data-gen.sh                        | Generate test data for all files     |
| run.sh                             | Compile, run, verify                 |
| README.md                          | This file                            |

## Data Design

- master.dat: 5 records -- 3 with KEY00001, 2 with KEY00002
- detail.dat: 2 records -- KEY00001, KEY00002 (one per master group)
- final-ref.dat: 1 record -- KEY00001 only

Stage 1: 5 masters -> 2 intermediate records (N:1, one per matching group)
Stage 2: 2 intermediate -> 1 final output (only KEY00001 matches final-ref)

## Expected Behavior

- Stage 1 matches each master group to one detail record (N:1), writing
  one temp record per group that has a matching detail.
- Stage 2 matches each temp record against the final reference, writing
  one output per matching temp group.
- Final output: 1 record (only KEY00001 group matches final-ref).