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Gerwin Hendriksen
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Company profile
Back to HOTSOS, HOTSOS 2010 Day 1
As always Hotsos started off with a nice keynote, this time done by Tom Kyte. Tom Kyte was introduced by Hotsos president Gary Goodman after the HOTSOS 2010 opening. Tom’s keynote theme was “Should we be less smart some times”. Tom told about own experiences, that he in the past gave sometimes too fast an answer. It is very important to think about an answer before giving it… Why? Well some things applied in the past or for a specific version, and now they don’t anymore… this can be a problem, a real issue. Always make sure you talk about the same definitions, and agree on them. Make sure talking about the same version and of course about similar circumstances. When you start giving answers in general be sure to work with facts and not some assumptions which might be wrong. So you should always think about the information, about the circumstances and the assumptions you do, it means “Continuous Thinking”.
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How to change an outerjoin query to one without
Some time ago I encountered an issue with an outerjoin query. Although the execution plan was not that bad the respons time was really bad. I found out that the outerjoin in the query was causing the biggest problem. After doing some easy research I checked out the performance of a query with a direct join (a.col = b.col) and one without a join (a.col is not joined). Even if you would execute them seperate you would be much faster as doing the outerjoin. This brought me to the idea of doing these two queries for the sake of the data be retrieved by the outerjoin. By doing a union between these two queries and to get rid of the double records, I would have the same result as with the outerjoin. This is what I did, a collaegae of mine Jorrit Nijssen changed the code to a emp/dept example (thanks Jorrit). The base case looks like: Read more