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#21
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I'm in the fortunate position of not having any time pressure on this
project so I can take the time to do it 'right'. But then on the other hand, I have to fit this into free time between work and home - so development is very slow and sometimes I have to 're-learn' how to do things. A project with no "time pressure"? Is that really a project? g I must have a different book than you (or maybe I got the title wrong?) - I thought that this one's by Michael Hernandez. Yes, Michael wrote the one you are referring to. I'm reading Rebecca Riordan's Designing Relational Database Systems right now and had it on my brain. Sorry about that. Apologies to Michael and Rebecca too, for confusing them g. -- Lynn Trapp MS Access MVP www.ltcomputerdesigns.com Access Security: www.ltcomputerdesigns.com/Security.htm "rpw" wrote in message ... "Lynn Trapp" wrote: You may find that a Google search on "surrogate keys" would return you some interesting, and lively, discussions of the subject. I'll do that later on today... You should probably reconsider the advice of the local user group. By allowing the employees to enter duplicates, you not only violate one of the cardinal principles of database design, but make more work for you payroll department, when they have to track down the employee who entered the duplicate. I assume after they talk to this employee that they then have to go out and delete the duplicate record. Wouldn't it be better to find a way to preven its entry in the first place? I'll keep working on that. In the meantime I looked at my db again and the 'duplicates' are not actually duplicate records, but rather multiple entries on the same day by the same employee. This could have happened for any number of reasons. As I study this issue deeper, I'll consider the indexing of date, EmpID, (maybe start and end times too) vs. combination key. I'm in the fortunate position of not having any time pressure on this project so I can take the time to do it 'right'. But then on the other hand, I have to fit this into free time between work and home - so development is very slow and sometimes I have to 're-learn' how to do things. btw, on Saturday I got delivery of "Database Design for Mere Mortals", so maybe by the time I finish reading it, I'll be a little better oriented on these 'Natural key, combo key, surrogate key issues. But for now, I still like the convenience of using just a single PK field. That's excellent. Rebecca has an excellent discussion of "candidate keys" in a real world context and in easy to understand language. She seems to lean in favor of surrogate keys but not without a proper understanding of data duplication. I must have a different book than you (or maybe I got the title wrong?) - I thought that this one's by Michael Hernandez. -- Lynn Trapp MS Access MVP www.ltcomputerdesigns.com Access Security: www.ltcomputerdesigns.com/Security.htm |
#22
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"Lynn Trapp" wrote: A project with no "time pressure"? Is that really a project? g I'd be happy to send you version one and version two if you like. by the way, I assigned myself this 'project' cause the things I saw in the books didn't have any relevance to me and this did. The project will be useful to my employer, but the company doesn't know I'm working on it - hence no time pressure. I'll be sure to keep Ms. Riordan's book in mind when I'm hungry for more db design knowledge. I must have a different book than you (or maybe I got the title wrong?) - I thought that this one's by Michael Hernandez. Yes, Michael wrote the one you are referring to. I'm reading Rebecca Riordan's Designing Relational Database Systems right now and had it on my brain. Sorry about that. Apologies to Michael and Rebecca too, for confusing them g. -- Lynn Trapp MS Access MVP www.ltcomputerdesigns.com Access Security: www.ltcomputerdesigns.com/Security.htm "rpw" wrote in message ... "Lynn Trapp" wrote: You may find that a Google search on "surrogate keys" would return you some interesting, and lively, discussions of the subject. I'll do that later on today... You should probably reconsider the advice of the local user group. By allowing the employees to enter duplicates, you not only violate one of the cardinal principles of database design, but make more work for you payroll department, when they have to track down the employee who entered the duplicate. I assume after they talk to this employee that they then have to go out and delete the duplicate record. Wouldn't it be better to find a way to preven its entry in the first place? I'll keep working on that. In the meantime I looked at my db again and the 'duplicates' are not actually duplicate records, but rather multiple entries on the same day by the same employee. This could have happened for any number of reasons. As I study this issue deeper, I'll consider the indexing of date, EmpID, (maybe start and end times too) vs. combination key. I'm in the fortunate position of not having any time pressure on this project so I can take the time to do it 'right'. But then on the other hand, I have to fit this into free time between work and home - so development is very slow and sometimes I have to 're-learn' how to do things. btw, on Saturday I got delivery of "Database Design for Mere Mortals", so maybe by the time I finish reading it, I'll be a little better oriented on these 'Natural key, combo key, surrogate key issues. But for now, I still like the convenience of using just a single PK field. That's excellent. Rebecca has an excellent discussion of "candidate keys" in a real world context and in easy to understand language. She seems to lean in favor of surrogate keys but not without a proper understanding of data duplication. I must have a different book than you (or maybe I got the title wrong?) - I thought that this one's by Michael Hernandez. -- Lynn Trapp MS Access MVP www.ltcomputerdesigns.com Access Security: www.ltcomputerdesigns.com/Security.htm |
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