Category Archives: SQL

Constraints

The other day a friend called me with a question on constraints. “I have a table where the combination of two columns must be unique”. My response was: “Use a Unique Constraint on these two columns”.That should work, however…

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Log errors

Just a quick note of something I ran into at my current assignment. I have to import data from external tables into persistent tables. This proces normally is just inserting data into the table, but sometimes a file can be sent in more than once.

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Recursive Subquery

At my current assignment we are processing files coming from an online system to be inserted into our database (kind of a data warehouse). This is done using external tables and a scheduled job. The job just checks if there is a file available and will process this. The trouble is that the files might […]

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Comparing queries…

How do you compare a rewritten query to its original version? Most of the time I just run a MINUS operation on the original and new query. Actually I execute two. Old query (A) MINUS New query (B) and vice versa (B) MINUS (A). Both should result in no rows. That way I thought I […]

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