92 lines
4.4 KiB
Plaintext
92 lines
4.4 KiB
Plaintext
---
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title: Field Lineage
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description: Analyze upstream, downstream, and potential column impact from foreign keys, view definitions, query history, and matching names.
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---
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Field lineage helps answer where a column comes from, where it is used, and what a change might affect. DBX combines database metadata with local query history and labels evidence strength instead of treating every matching name as a confirmed dependency.
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## Open Lineage
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Open field lineage from a column node, table structure, or related context menu. The active column becomes the target, and results list related tables, columns, views, or historical SQL.
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## Relationship Sources and Confidence
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| Source | Default confidence | Meaning |
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| --- | --- | --- |
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| Foreign key | Certain | The database declares a constraint between the current and target columns |
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| View definition | Likely or possible | Confidence is higher when view source references both the target table and column |
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| Query history | Likely or possible | Historical SQL is stronger evidence when both table and column are present |
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| Same-name column | Possible | Name-based inference only and requires business confirmation |
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The UI distinguishes **Certain**, **Likely**, and **Possible**. Filter lower-confidence results to focus on foreign keys and explicit source references first.
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## Search and Filters
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- Search tables, columns, views, or SQL fragments
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- Filter by confidence
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- See displayed and total relationship counts
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- Copy table or column names
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- Open target table data or structure
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- Reveal the related object in the tree
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Lineage loads foreign keys, view source, and related metadata according to database capability. Initial analysis can take time in large schemas.
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## Query History as Evidence
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DBX uses executed queries as supporting evidence, including:
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- Fields that appear together in a `JOIN`
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- Target columns referenced in `WHERE`, `SELECT`, or expressions
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- Historical repair or reporting SQL that uses a matching field
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History only represents SQL executed or saved in DBX. It does not cover all application code, ETL, BI, or other clients.
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<Callout type="warn">Query history can contain sensitive table names, predicates, and literals. Review privacy before demonstrating lineage, exporting logs, or sharing screenshots.</Callout>
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## View and Source Analysis
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View relationships use definitions returned by the database. Confidence can be lower with:
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- Dynamic SQL or generated procedure text
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- Ambiguous tables or columns without explicit schema
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- `SELECT *`, complex subqueries, or vendor extensions
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- Databases that do not return complete view source
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Open a view result and inspect source in [Object Browser](/en/docs/object-browser) for manual confirmation.
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## Workflows
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### Before Changing a Column
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1. Review confirmed foreign-key relationships
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2. Inspect likely views and historical SQL
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3. Validate possible same-name relationships with business context
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4. Continue searching application repositories, ETL, and BI assets
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5. Use [Schema Diff](/en/docs/schema-diff) to review target-environment changes
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### Understanding an Unfamiliar Database
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Start with primary keys, business identifiers, user IDs, or time columns and follow related tables and views. Column comments and object source are usually stronger evidence than name matching alone.
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## Support and Boundaries
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- Lineage requires foreign keys, view source, or parseable query history, so coverage varies by database
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- Without declared foreign keys, DBX can only provide view, history, and same-name clues
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- Results are not a strongly consistent data-governance graph and do not include every application, message flow, ETL, or BI system
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- Deleting history or clearing local data reduces the query-history source
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- Use the [Database Support](/en/docs/databases) matrix for current engine coverage
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<Callout type="info">Important schema changes still need database constraints, source review, application-code search, and business-owner confirmation. Lineage narrows the investigation; it does not replace impact analysis.</Callout>
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<Cards>
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<Card title="Schema browser" href="/en/docs/schema-browser">
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Inspect columns, foreign keys, comments, and object hierarchy.
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</Card>
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<Card title="Object source" href="/en/docs/object-browser">
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Inspect view, procedure, function, and trigger definitions.
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</Card>
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<Card title="Schema diff" href="/en/docs/schema-diff">
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Review environment differences and deployment scripts.
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</Card>
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</Cards>
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