December 2010
Intermediate to advanced
451 pages
11h 16m
English
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2-15. Finding and Removing Duplicate Table Rows
Problem
You have found that for some reason your database contains a table that has duplicate records. You are working with a database that unfortunately does not use primary key values, so you must manually enforce data integrity. You need a way to remove the duplicate records. However, any query you write to remove one record will also remove its duplicate.
Solution
The solution to this issue involves two steps. First you need to query the database to find all duplicate rows, and then you need to run a statement to delete one of each duplicate record that is found.
The following code block queries the EMPLOYEES table for duplicate rows. When a duplicate is found, it is returned along with a count ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.