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Locating Data Discrepenciesgood things though and was hoping that before i dive into a project I may gain some advice on the task at hand. What I'm trying to do is develop some sort of exception report which isolates inconsistent data between two or more similar records i.e. I have two records, let's assume the following fields for each record. id, ImportDate, TargetValue, value1, value2, value3, value4, and value5 Sample data is as such: ABC, 9/5/2006, 100, A, B, C, D, E ABC, 9/1/2006, 101, A, C, C, D, E the fields value1:Value5 impact the difference between the field TargetValue Understanding this, looking at field Value2 one can quickly determine the difference here is what caused the change between the TargetValue values between 9/1/2006 and 9/5/2006. With this example isolating the differences is not that difficult and I could probably handle in a fairly straight forward procedure, most likely joining on each of the values until there is a variance. However, it isn't this easy as I'm going to have to isolate differences between records on nearly a 150 fields on up to thousands of records. Ideally I would like to create (don't know that i can do this exclusively in SQL or not, thus the question) a report that will identify any area where the TargetValue is different between two similar records as well as only the fields where the value(s) responsible for the change are reported. Any ideas, is this feasable? Any help or ideas are greatly appreciated. Thanks. -- Message posted via SQLMonster.com http://www.sqlmonster.com/Uwe/Forums.aspx/sql-server-programming/200609/1 On Tue, 05 Sep 2006 21:47:09 GMT, jmancuso via SQLMonster.com wrote:
(snip) >With this example isolating the differences is not that difficult and I could Hi jmancuso,>probably handle in a fairly straight forward procedure, most likely joining >on each of the values until there is a variance. > >However, it isn't this easy as I'm going to have to isolate differences >between records on nearly a 150 fields on up to thousands of records. If you have 150 columns, you'll have to consider seriously if your table design is normalized. Note that I'm not saying it's not: there are examples of normalized tables with lots of columns. For instance a complete physical might inculde measurements of length, weight, heart rate, blood pressure, lung capacity, hemoglobin, etc, etc. All different attributes that can all be combined into a single table. But even though such situations do exist, I'm afraid that the majority of 50+-column tables are just bad design. If, for example, the 150 columns are 5 different measurements taken on each day of the month, then you should add day number as an extra column, include it in the primary key, and remove all but 1 column for each of the 5 measurements. >Ideally I would like to create (don't know that i can do this exclusively in You pprobably can do it in SQL, but remember that SQL was designed as a>SQL or not, thus the question) a report that will identify any area where the >TargetValue is different between two similar records as well as only the >fields where the value(s) responsible for the change are reported. language for manipulating large quantities of data, not as a language for creating reports. Almost every language will be better suited for this task than SQL. Just fetch the rough data from SQL Server into the front end, compare the data there and create the report based on the comparison results. And remember to handle NULL properly in your comparison. If the data can allow NULL, then you won't find all differences with WHERE a.Column1 <> b.Column1 You'll have to cater for changes from NULL to non-NULL and vice versa as well: WHERE a.Column1 <> b.Column1 OR (a.Column1 IS NULL AND b.Column1 IS NOT NULL) OR (a.Column1 IS NOT NULL AND b.Column1 IS NULL) How you do that in your reporting language depends on how NULL is represented in that language and how the language deals with comparisons involving NULL. -- Hugo Kornelis, SQL Server MVP try firefly sql compare. i wrote it for this purpose, it's free.
http://www.getfirefly.net/ http://www.getfirefly.net/FF_Screen_1_Small_4.png |
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