Avoiding IF.. ELSE by using WHERE EXISTS
When coming from a programming background, it’s natural to want to frame conditional operations within the familiar if.. else constructs. This happens in a lot of SQL code I have worked with (and I...
View ArticleCompare Stored Procedure Output by Creating a Test Harness
When optimizing procedures often times you need to rewrite the procedure in order to speed it up. However, when you’re finished how can you be sure that the result set is still the same? This article...
View ArticleA Query Method Faster Than BETWEEN
This is an invaluable trick that can be sometimes be used instead of the BETWEEN operator. A common place this can be used is in an historical table that contains EffectiveFrom & EffectiveTo dates....
View ArticleOvercome Divide by Zero Using NULLIF
Anytime we are dividing we need to think of the divide by zero scenario. Even if you think you will never encounter this with your result set, it’s advisable to guard against it because when divide by...
View ArticleUser Defined Functions and Performance
There is definitely a lack of awareness in the SQL world regarding the use of user defined functions and the potential performance hit they can have when using within your queries. Don’t get me wrong,...
View ArticleUsing the OUTPUT Clause in SQL Server
The OUTPUT clause in SQL Server 2008 was probably one of the most functional T-SQL enhancements added. I personally don’t use it enough because I often forget about it, however I have used it to...
View ArticleMatch identity columns after INSERT
One common requirement in SQL when inserting data between tables is to match the new identity column with the old identity column. The most common solution to this problem is to perform a cursor and do...
View ArticleDelete Using INNER JOIN
The need to join tables in order to determine which records to delete is a common requirement. The syntax can be somewhat tricky because you need to use an alias for the table you want to delete from....
View ArticleFormat String to Date
Changing the datatype of a string that represents a date to an actual date datatype is relatively easy using the CAST function. As long as the date string is in a format recognizable to the regional...
View ArticleUsing WHERE EXISTS
As you may know, the WHERE EXISTS clause is used to constrain records from an outer query with records from an inner query. What does that mean? It’s just another way to say “it limits the result set”....
View ArticleMulti Row Insert
Performing a multi-row insert got easier in SQL 2008. A new syntax was added to accomodate multiple rows when using the VALUES statement. This code will only work in 2008+. In order to accomplish the...
View ArticleDrop Table if Exists
To determine if a table exists, it’s best to go against the sys.objects view by querying the object_id using the fully qualified name of the table. The additional ‘type’ field in the where clause...
View ArticleSelecting 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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User Defined Functions and Performance
There is definitely a lack of awareness in the SQL world regarding the use of user defined functions and the potential performance hit they can have when using within your queries. Don’t get me wrong,...
View ArticleUsing the OUTPUT Clause in SQL Server
The OUTPUT clause in SQL Server 2008 was probably one of the most functional T-SQL enhancements added. I personally don’t use it enough because I often forget about it, however I have used it to...
View ArticleMatch identity columns after INSERT
One common requirement in SQL when inserting data between tables is to match the new identity column with the old identity column. The most common solution to this problem is to perform a cursor and do...
View ArticleDelete Using INNER JOIN
The need to join tables in order to determine which records to delete is a common requirement. The syntax can be somewhat tricky because you need to use an alias for the table you want to delete from....
View ArticleFormat String to Date
Changing the datatype of a string that represents a date to an actual date datatype is relatively easy using the CAST function. As long as the date string is in a format recognizable to the regional...
View ArticleClik here to view.
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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