Table of Contents

Search

  1. Preface
  2. Transformations
  3. Source transformation
  4. Target transformation
  5. Aggregator transformation
  6. Cleanse transformation
  7. Data Masking transformation
  8. Data Services transformation
  9. Deduplicate transformation
  10. Expression transformation
  11. Filter transformation
  12. Hierarchy Builder transformation
  13. Hierarchy Parser transformation
  14. Hierarchy Processor transformation
  15. Input transformation
  16. Java transformation
  17. Java transformation API reference
  18. Joiner transformation
  19. Labeler transformation
  20. Lookup transformation
  21. Machine Learning transformation
  22. Mapplet transformation
  23. Normalizer transformation
  24. Output transformation
  25. Parse transformation
  26. Python transformation
  27. Rank transformation
  28. Router transformation
  29. Rule Specification transformation
  30. Sequence Generator transformation
  31. Sorter transformation
  32. SQL transformation
  33. Structure Parser transformation
  34. Transaction Control transformation
  35. Union transformation
  36. Velocity transformation
  37. Verifier transformation
  38. Web Services transformation

Transformations

Transformations

Lookup transformation

Lookup transformation

Use a Lookup transformation to retrieve data based on a specified lookup condition. For example, you can use a Lookup transformation to retrieve values from a database table for codes used in source data.
When a
mapping
task includes a Lookup transformation, the task queries the lookup source based on the lookup fields and a lookup condition. The Lookup transformation returns the result of the lookup to the target or another transformation. You can configure the Lookup transformation to return a single row or multiple rows. When you configure the Lookup transformation to return a single row, the Lookup transformation is a passive transformation. When you configure the Lookup transformation to return multiple rows, the Lookup transformation is an active transformation.
You can use multiple Lookup transformations in a mapping.
In advanced mode, you can perform lookups only on sources that an
advanced cluster
can process.
Perform the following tasks with a Lookup transformation:
  • Get a related value. Retrieve a value from the lookup table based on a value in the source. For example, the source has an employee ID. Retrieve the employee name from the lookup table.
  • Get multiple values. Retrieve multiple rows from a lookup table. For example, return all employees in a department.
  • Update slowly changing dimension tables. Determine whether rows exist in a target.
You can perform the following types of lookups:
Connected or unconnected lookup
A connected Lookup transformation receives source data, performs a lookup, and returns data.
An unconnected Lookup transformation is not connected to a source or target. A transformation calls the Lookup transformation with a lookup expression. The unconnected Lookup transformation returns one column to the calling transformation.
Cached or uncached lookup
Cache the lookup source to optimize performance. If you cache the lookup source, you can use a static or dynamic cache. You can also use a persistent or non-persistent cache.
By default, the lookup cache remains static and does not change as the
mapping
task runs. With a dynamic cache, the task inserts or updates rows in the cache as the target table changes. When you cache the target table as the lookup source, you can look up values in the cache to determine if the values exist in the target.
By default, the lookup cache is also non-persistent. Therefore,
Data Integration
deletes the cache files after the
mapping
task completes. If the lookup table does not change between mapping runs, you can use a persistent cache to increase performance.

0 COMMENTS

We’d like to hear from you!