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Schema Mapping Document
Project: [project or migration name]
Source system: [system name / table]
Target system: [system name / table]
Analyst: [name]
Date: [YYYY-MM-DD]
Version: [1.0]
Overview
Purpose of mapping: [Why this mapping is being created — migration, integration, new data model]
Total source columns: [n]
Total target columns: [n]
Direct matches: [n]
Requiring transformation: [n]
Target columns with no source: [n]
Column mapping
| Source column |
Source type |
Target column |
Target type |
Transformation |
Notes |
| source.col_a |
VARCHAR |
target.col_a |
VARCHAR |
Direct |
— |
| source.col_b |
INTEGER |
target.amount_usd |
DECIMAL |
col_b / 100.0 |
Convert cents to dollars |
| source.first_name + last_name |
VARCHAR |
target.full_name |
VARCHAR |
CONCAT(first_name, ' ', last_name) |
— |
| source.col_c |
TIMESTAMP |
target.event_date |
DATE |
DATE(col_c) |
Time component dropped |
| — |
— |
target.created_at |
TIMESTAMP |
CURRENT_TIMESTAMP |
System-generated on insert |
| source.legacy_flag |
BOOLEAN |
(dropped) |
— |
Not included in target |
Deprecated |
Unmapped target columns (need derivation or default)
| Target column |
Type |
Derivation plan |
Owner |
Status |
| [column] |
[type] |
[how to populate] |
[owner] |
[open/resolved] |
Type mismatch summary
| Column |
Source type |
Target type |
Required CAST |
Risk |
| [column] |
[type] |
[type] |
CAST(col AS target_type) |
[truncation / precision loss / format error] |
Validation rules
| Target column |
Rule |
Test query |
| [column] |
NOT NULL |
SELECT COUNT(*) FROM target WHERE col IS NULL |
| [column] |
Value in accepted set |
SELECT DISTINCT col FROM target WHERE col NOT IN ('a','b','c') |
| [column] |
Referential integrity |
SELECT * FROM target t LEFT JOIN dim d ON t.fk = d.pk WHERE d.pk IS NULL |
Sign-off
| Role |
Name |
Date |
Status |
| Source data owner |
|
|
|
| Target schema owner |
|
|
|
| Engineering lead |
|
|
|
| Analytics reviewer |
|
|
|
Template: schema_mapping_template.md
