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Articles with tag constraints Rss

Search for any content tagged constraints

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Leveraging Constraint Evaluation Sequence in SQL Server

Constraints on a table in SQL Server are evaluated in a specific sequence. Knowing this sequence can help us leverage them to realize various business requirements.  Read more...
By Nakul Vachhrajani 2014/01/27 | Source: SQLServerCentral.com | Category: sql server
Rating: |  Discuss |   Briefcase | 2,598 reads

Handling Constraint Violations and Errors in SQL Server

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...
By Additional Articles 2012/07/10 | Source: SimpleTalk | Category: constraints
Rating: (not yet rated)  Rate this |   Briefcase | 3,078 reads

Constraints and the Test-Driven Database

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...
By Additional Articles 2012/01/09 | Source: SimpleTalk | Category: database design
Rating: (not yet rated)  Rate this |   Briefcase | 1,890 reads

Primary Keys – why accept the defaults.

G’day, When I design a table in SQL SERVER, I like to have a reasonable understanding of how the table will...  Read more...
By Martin Catherall 2011/03/22 | Source: SQLServerCentral.com | Category: blogs
Rating: (not yet rated)  Rate this |   Briefcase | 2,402 reads

SQL Server Unique Constraints for Large Text Columns

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...
By Additional Articles 2009/11/05 | Source: MSSQLTips.com | Category: constraints
Rating:  Rate this |   Briefcase | 2,591 reads

Constraint Yourself!

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...
By Additional Articles 2008/10/30 | Source: SimpleTalk | Category: database design
Rating:  Rate this |   Briefcase | 2,430 reads

Should I Use a UNIQUE Constraint or a Unique Index in SQL Server?

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...
By Additional Articles 2008/09/05 | Source: MSSQLTips.com | Category: constraints
Rating:  Rate this |   Briefcase | 7,557 reads

Comparing SQL Server constraints and DML triggers

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...
By Additional Articles 2008/07/23 | Source: Builder.com | Category: triggers
Rating:  Rate this |   Briefcase | 2,511 reads

Avoid Untrusted Constraints in SQL Server

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 Additional Articles 2008/07/18 | Source: MSSQLTips.com | Category: referential integrity
Rating:  Rate this |   Briefcase | 2,668 reads

Defining cascading referential integrity constraints in SQL Server

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...
By Additional Articles 2008/06/20 | Source: Builder.com | Category: dri
Rating: (not yet rated)  Rate this |   Briefcase | 2,208 reads
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