Why does DB-adapter return duplicate rows? by Jon Petter Hjulstad

 

clip_image002Here are some DB adapter tips regarding duplicate rows.

The DB Adapter has some nice features, but sometimes you can get fooled. One of my colleagues experiences this one day. The query returned the same row – just repeated many times.

The reason for this is because the primary key was not defined correctly.

The good thing is that the documentation describes this – and more: Oracle documentation

For tables where primary key is defined – this should not be a problem, but in cases where it is not defined or you are querying a view – you would need to specify a primary key yourself. A couple of relevant notes here:

  • If you do not provide a valid primary key, then the unique constraint is not guaranteed, and this could result in possible loss of messages at runtime. That is, rows with duplicate primary key values are likely to be lost.
  • You should ensure that you primary key is less than 100 bytes.
  • Oracle recommends that you use varchar instead of char for primary key columns

Read the complete article here.

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About Jürgen Kress
As a middleware expert Jürgen works at Oracle EMEA Alliances and Channels, responsible for Oracle’s EMEA Fusion Middleware partner business. He is the founder of the Oracle SOA & BPM and the WebLogic Partner Communities and the global Oracle Partner Advisory Councils. With more than 5000 members from all over the world the Middleware Partner Community is the most successful and active community at Oracle. Jürgen manages the community with monthly newsletters, webcasts and conferences. He hosts his annual Fusion Middleware Partner Community Forums and the Fusion Middleware Summer Camps, where more than 200 partners get product updates, roadmap insights and hands-on trainings. Supplemented by many web 2.0 tools like twitter, discussion forums, online communities, blogs and wikis. For the SOA & Cloud Symposium by Thomas Erl, Jürgen is a member of the steering board. He is also a frequent speaker at conferences like the SOA & BPM Integration Days, JAX, UKOUG, OUGN, or OOP.

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