# 22-matching-2stage-MN: Two-Stage M:N Matching

## 电信业务场景

二级套餐匹配。两段M:N匹配。第一段:基本套餐匹配；第二段:附加套餐匹配。用于叠加套餐的计费处理。

This test verifies two-stage M:N (Cartesian product) matching behavior.

## Algorithm

**Stage 1:** Read FILE-A (`file-a.dat`) and FILE-B (`file-b.dat`), write matched records to TEMP-FILE (`temp.dat`). For each matching key, outputs A_count x B_count records (Cartesian product).

**Stage 2:** Read TEMP-FILE (`temp.dat`) and FILE-C (`file-c.dat`), write matched records to FINAL-OUT (`final.dat`). For each matching key, outputs temp_count x C_count records (Cartesian product).

## Test Data

### file-a.dat (4 records)
- KEY00001: 2 records
- KEY00002: 2 records

### file-b.dat (3 records)
- KEY00001: 2 records
- KEY00003: 1 record

### file-c.dat (4 records)
- KEY00001: 2 records
- KEY00002: 2 records

## Expected Results

**Stage 1:** KEY00001 matches (2x2=4 temp records)
- KEY00002 has no B match (skipped)
- KEY00003 has no A match (skipped)
- Total: 4 records in temp.dat (180 bytes)

**Stage 2:** 4 temp records (KEY00001) x 2 file-c records (KEY00001) = 8 output records
- Total: 8 records in final.dat (360 bytes)

## Files
- `main-22-matching-2stage-MN.cbl` — COBOL program
- `data-gen.sh` — Test data generator
- `run.sh` — Compile, run, and verify script