# 35-merge — MERGE Processing Program

## 电信业务场景

多源CDR合并。使用MERGE语句将来自多个BSS系统的CDR文件(2~3个)合并为一个统合CDR文件，支持OUTPUT PROCEDURE。

## Purpose
Demonstrates COBOL MERGE statement capabilities, covering MR-N001 through MR-N004 and MR-A001.

## Test Coverage
| ID | Test | Description |
|----|------|-------------|
| MR-N001 | 2-file MERGE | Merge two sorted files, ASCENDING KEY |
| MR-N002 | 3-file MERGE | Merge three sorted files into one |
| MR-N003 | Duplicate key MERGE | Files with overlapping keys |
| MR-N004 | OUTPUT PROCEDURE | MERGE with output procedure processing |
| MR-A001 | Unsorted input anomaly | MERGE with unsorted input (expected unpredictable results) |

## Key Techniques
- MERGE USING (multiple input files)
- MERGE GIVING (direct output)
- MERGE with OUTPUT PROCEDURE
- RETURN statement in output procedure
- ASCENDING KEY for merge ordering
- Note: MERGE requires pre-sorted input files