I would like to determine the values that are different between a composite foreign key and composite primary key. I cannot currently create this relationship because there are values in the child table that are not in the parent table. The foreign key is:
ALTER TABLE EDI.HM_MCSMD ADD CONSTRAINT HM_MCSMD_02_FK FOREIGN KEY ( TPR_PCSG_CO_ID , MXFG_ID , MCSMS_TRNS_HDR_ID , MCSMS_MVEI_ID ) REFERENCES EDI.HM_MCSMS ( TPR_PCSG_CO_ID , MXFG_ID , MCSMS_TRNS_HDR_ID , MCSMS_MVEI_ID ) ENABLE
You need to investigate and fix these anomalies, perhaps by deleting the child rows, or adding the parent rows that are missing. Here's the query to find them:
select TPR_PCSG_CO_ID , MXFG_ID , MCSMS_TRNS_HDR_ID , MCSMS_MVEI_ID from EDI.HM_MCSMD as D where not exists ( select 1 from EDI.HM_MCSMS where TPR_PCSG_CO_ID = D.TPR_PCSG_CO_ID and MXFG_ID = D.MXFG_ID and MCSMS_TRNS_HDR_ID = D.MCSMS_TRNS_HDR_ID and MCSMS_MVEI_ID = D.MCSMS_MVEI_ID )
There are a number of ways to write a query to find missing related rows, but I like NOT EXISTS with a correlated subquery because it says what you want. Well, except for the SELECT 1 bit, but that's another story (see How does WHERE EXISTS ( SELECT NULL... ) work? 22 February 2002).
If your decision to fix the anomalies is to delete the orphans, just change the query above to say DELETE FROM instead of SELECT ... FROM.
On the other hand, if you will be creating parent rows for the orphans to relate to, feed the query above into an INSERT statement:
insert into EDI.HM_MCSMS ( TPR_PCSG_CO_ID , MXFG_ID , MCSMS_TRNS_HDR_ID , MCSMS_MVEI_ID ) select ...
The insert will only work if all the other columns in the parent table, i.e. the non-key columns not mentioned in the INSERT column list, have default values or are allowed to go null.
For More Information
- Dozens more answers to tough SQL questions from Rudy Limeback.
- The Best SQL Web Links: tips, tutorials, scripts, and more.
- Have an SQL tip to offer your fellow DBAs and developers? The best tips submitted will receive a cool prize. Submit your tip today!
- Ask your technical SQL questions -- or help out your peers by answering them -- in our live discussion forums.
- Ask the Experts yourself: Our SQL, database design, Oracle, SQL Server, DB2, metadata, object-oriented and data warehousing gurus are waiting to answer your toughest questions.
Dig Deeper on Oracle and SQL
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.