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The database developer can, of course, throw all errors back to the application developer to deal with, but this is neither kind nor necessary. How errors are dealt with is dependent on the application, but the process itself isn't entirely obvious.  Read more...

Bad data always seems to appear when, and where, one least expects it. Sam explains the great value of a defensive approach based on constraints to any team that is developing an application in which the data has to be exactly right, and where bad data could cause consequential severe financial damage. It is perhaps better seen as creating a test-driven database.  Read more...

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G’day, When I design a table in SQL SERVER, I like to have a reasonable understanding of how the table will...  Read more...

This stored procedure can be used for applying a custom column check constraint naming convention  Read more...

This stored procedure can be used for applying a custom foreign key constraint naming  Read more...

This stored procedure can be used for applying a custom default constraint naming  Read more...

This stored procedure can be used for applying a custom default constraint naming  Read more...

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We are storing large text and URLs that are over 900 bytes in some of our tables and have a requirement to enforce uniqueness in those columns. But SQL Server has a limitation that index size can't be over 900 bytes. How do I enforce uniqueness in these columns and is it possible to achieve this in SQL Server 2005 and above? What are my different options to solve this problem? I heard that we can use CHECKSUM to create a hash, but is it possible to avoid collisions in the hash value as we are storing millions of rows?  Read more...

In his first article for Simple-Talk, Joe Celko demystifies the use of Constraints, and points out that they are an intrinsic part of SQL and are a great way of ensuring that a business rule is done one way, one place, one time.  Read more...

I am modifying a table and I need to add a column that must be defined as being unique. I see that SQL Server allows you to define a UNIQUE constraint on a column but I also see that you can create a unique index on a column. Which one should I use?  Read more...

Over the years, I have witnessed many developers being confused about when to use data-manipulation language (DML) triggers vs. when to use constraints.  Read more...

Some time ago, I loaded a large set of data into one my tables. To speed up the load, I disabled the FOREIGN KEY and CHECK constraints on the table and then re-enabled them after the load was complete. I am now finding that some of the loaded data was referentially invalid. What happened?  Read more...

By using cascading referential integrity constraints, you can define the actions that SQL Server 2005 takes when a user tries to delete or update a key to which existing foreign keys point.  Read more...