Selecting Top N Records per Group
When you have multiple rows for let’s say a productID, there will probably be times when you need to select the top n subset of each those productid’s based upon a sort criteria. This is a relatively...
View ArticleSubstring Between Two Characters
Though SQL may not be the most elegant language for string handling, it does perform most functions and in a set based manner. The SQL substring function basically has the same syntax as found in other...
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How to order numeric values in a varchar field
If you have ever tried to order numerical values in a varchar field you’ll know that the sort doesn’t occur numerically as it would if the datatype were numeric. In other words, the values of 1 and 10...
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Using WITH (NOLOCK)
The WITH (nolock) hint is an explicit command directed at a specific table or view used to set the transaction isolation level against the table or tables within a view for a specific query. Once...
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The Difference Between UNION and UNION ALL
If you’re like me, after using UNION for many years you may have stumbled upon the UNION ALL and thought, what the heck is the difference? Well it’s pretty simple. UNION gives you the unique results...
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Yet Another Temp Tables Vs Table Variables Article
The debate whether to use temp tables or table variables is an old debate that goes back since they were first introduced. The real answer to knowing the difference lies in what is going on under the...
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Comparing EXISTS vs LEFT JOIN WHERE NOT NULL
Two of the most common ways to check for the existence of records is to use a WHERE EXISTS or to perform a LEFT JOIN WHERE values are NOT NULL. My personal choice is usually to use the EXISTS method...
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Top 3 SQL Errors That Will Leave Your Users Stranded
Over the years I’ve ran across certain situations that cause errors in SQL that error out the calling application if they are not correctly trapped. As unsuspecting as these can be, you end up learning...
View ArticleCTE’s vs Temp tables – an Opinion
This is one of those topics that will get people fired up. But here goes. I am mostly an explicit temp table developer. By contrast, I am not an implicit temp table developer. What I mean by that is –...
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Convert Int to String
There are two different functions that can be used when converting an integer to a string. One is CAST and the other is CONVERT. Either of these functions can be used with the exact same result when...
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