# 23-select-condition — SELECT Condition Simulation

## 电信业务场景

客户合同检索。使用索引文件模拟SELECT条件检索，通过START+READ NEXT实现条件匹配和范围查询。

## Purpose
Simulates SQL SELECT with WHERE conditions using GnuCOBOL INDEXED files and START/READ NEXT operations.

## Test Coverage
1. **Single record by key** — READ with KEY IS (exact match WHERE)
2. **Range query** — START with NOT LESS THAN, loop with upper bound check
3. **Zero results** — Key not found, INVALID KEY handling
4. **Greater-than query** — START with GREATER THAN, read all following records

## Key Techniques
- INDEXED file ORGANIZATION with DYNAMIC access
- START for positioning (KEY IS GREATER THAN / NOT LESS THAN)
- READ NEXT for sequential traversal
- FILE STATUS checking
- INVALID KEY / NOT INVALID KEY for conditional handling