Monthly Archives: September 2013

External Tables

Oren Nakdimon 1 Reply

This is a feature I use a lot… An external table in Oracle is a table that its structure is defined in the data dictionary, but its content is taken from a standalone file, and is not stored inside the database. This feature is very useful as part of an ETL process, where you need […]

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Literals

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It is possible to specify a date value as a literal, like that: DATE ‘2013-08-29′ This instantiates a date constant, which is equivalent to the result of to_date(’29/08/2013′,’dd/mm/yyyy’) The date format in this case is always yyyy-mm-dd, and is not influenced by any parameter (the default format of the to_date function is defined by the […]

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The MERGE statement

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The SQL statement MERGE (available from version 9i) provides the functionality of “INSERT or UPDATE” in a single statement. The basic syntax is: MERGE INTO <target> USING <source> ON (<join conditions>) WHEN MATCHED THEN UPDATE <SET clause> WHEN NOT MATCHED THEN INSERT (<column list>) VALUES (<expression list>); where: <target> is the table that we’d like […]

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Course Addendum

Oren Nakdimon Leave a Reply

I lectured about Oracle SQL and PL/SQL in a course lately. As always, some issues that had not been part of the planned scope were raised and discussed, so I thought to write short posts about some of them, for the benefit of the participants and everyone else that may find it relevant. These issues […]

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