NB-076
38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
# 20-matching-MN-to-MxN
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## 电信业务场景
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CDR详细清单M:N→M×N。多个合同×多个通话明细的笛卡尔积组合，输出完整的CDR详细清单(M×N件)。
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**M:N matching — Cartesian product output (M x N records per matching key).**
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Tests the scenario where both input files may contain duplicate keys and
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every combination of matching master and detail records must be output
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(the full Cartesian product).
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## Test data
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| File | Records | Keys |
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|-------------|---------|------------------------------------------|
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| master.dat | 5 | KEY00001 (x2), KEY00002 (x1), KEY00003 (x2) |
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| detail.dat | 7 | KEY00001 (x3), KEY00003 (x2), KEY00004 (x2) |
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- **KEY00001:** 2 masters x 3 details = 6 output records
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- **KEY00003:** 2 masters x 2 details = 4 output records
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- **Total output:** 10 records
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- **Unmatched:** KEY00002 (master only), KEY00004 (detail only)
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## Algorithm
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1. Read both files synchronously (both assumed sorted by key).
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2. When keys match: read all master records for that key into a table,
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read all detail records for that key into a table, then write M x N
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output records covering every combination.
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3. Unmatched groups are skipped via the standard key-comparison logic.
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## Expected output
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- **output.dat:** 10 records x 45 bytes = 450 bytes
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- Program displays: `20-matching-MN-to-MxN: PASS`
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- Script displays: `20-matching-MN-to-MxN: ALL TESTS PASSED`
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