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From my code (Java) I want to ensure that a row exists in the database (DB2) after my code is executed.
My code now does a select and if no result is returned it does an insert. I really don't like this code since it exposes me to concurrency issues when running in a multi-threaded environment.
What I would like to do is to put this logic in DB2 instead of in my Java code. Does DB2 have an insert-or-update statement? Or anything like it that I can use?
For example:
insertupdate into mytable values ('myid') Another way of doing it would probably be to always do the insert and catch "SQL-code -803 primary key already exists", but I would like to avoid that if possible.
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The main difference between INSERT and UPDATE in SQL is that INSERT is used to add new records to the table while UPDATE is used to modify the existing records in the table.
No. Insert will only create a new row.
INSERT , UPDATE , and DELETE are all functions in SQL that help you ensure your data is up-to-date and kept clear of unnecessary or outdated information. INSERT , UPDATE , and DELETE , as well as SELECT and MERGE, are known as Data Manipulation Language (DML) statements, which let SQL users view and manage data.
Yes, DB2 has the MERGE statement, which will do an UPSERT (update or insert).
MERGE INTO target_table USING source_table ON match-condition {WHEN [NOT] MATCHED THEN [UPDATE SET ...|DELETE|INSERT VALUES ....|SIGNAL ...]} [ELSE IGNORE] See:
http://publib.boulder.ibm.com/infocenter/db2luw/v9/index.jsp?topic=/com.ibm.db2.udb.admin.doc/doc/r0010873.htm
https://www.ibm.com/support/knowledgecenter/en/SS6NHC/com.ibm.swg.im.dashdb.sql.ref.doc/doc/r0010873.html
https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/merge?lang=en
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