※ Download: Sql server composite primary key
True, this presents some challanges since codes can be dropped and later reused, because countries come and go. I certainly wouldn't use a surrogate in a case like this. In most applications where you deal with countries, you care about now-existing countries. Also read about database modeling and diagramming.
A clustered index is analogous to a telephone directory, which arranges data by last name. How this index will be organized? For this, we want to record which student took what class during what quarter, along with the date of registration, date of drop if the class was dropped , and the final grade.
- Then you can use a unique constraint, and SQL Server will reference it to enforce the foreign key constraint. You can't delete your own posts.
Sri I think you may be confusing primary key and clustered index here. When choosing a primary key, if one column uniquely identifies rows in the table, choose that. If you need a second column to make it unique, use a composite. If, on the other hand, you're choosing which column s to put your clustered index on, you need to do what works best for your data and the way you insert, modify and read it. I don't think we have enough information to make that judgement for you. All other things being equal which they rarely are , you want to keep your clustered index as narrow as possible for optimum performance. It is a good practice to use composite primary key where it is appropriate 2. It is a bad practice to use composite primary key where it is not appropriate 3. Cou can create nonclustered index on any column including idno 5. You can make PK to be non-clustered and create clustered key on other column, but I can't see that your sample has a case for this. I generally avoid composite primary keys, however, it depends.. I almost always build the primary clustered index on the single field that will always be unique. If my primary access to that table is through another field or fields, I may consider building the clustered index on that set of fields. Also, depending on the data and how its written it could be entirely likely that although you generally access it through the date that the idno is ok to be the primary clustered index and a non-clustered index on the date is ok. In the end a non-clustered index references the entries in the clustered index. CEWII You can't post new topics. You can't post topic replies. You can't post new polls. You can't post replies to polls. You can't edit your own topics. You can't delete your own topics. You can't edit other topics. You can't delete other topics. You can't edit your own posts. You can't edit other posts. You can't delete your own posts. You can't delete other posts. You can't post events. You can't edit your own events. You can't edit other events. You can't delete your own events. You can't delete other events. You can't send private messages. You can't send emails. You can read topics. You can't vote in polls. You can't upload attachments. You can download attachments. You can't post HTML code. You can't edit HTML code. You can't post IFCode. You can't post JavaScript. You can post emoticons. You can't post or upload images. Data Corruption Development Working with Oracle SQL Server 2005 Compact Edition SQL Server 2005 General Discussion SQL Server 2005 Security SQL Server 2005 Strategies SS2K5 Replication SQL Server Express SQL Server 2005 Performance Tuning SQL Server 2005 Integration Services T-SQL SS2K5 SQL Server Newbies SQL Server 7,2000 Administration Backups Data Corruption General Globalization In The Enterprise Working with Oracle Security Strategies SQL Server Newbies Service Packs SQL Server CE Performance Tuning Replication Sarbanes-Oxley T-SQL SQL Server Agent SQL Server and other platforms MySQL Oracle PostgreSQL DB2 SQL Server and Sharepoint Older Versions of SQL v6. Innovartis Embarcadero SQL Sentry Sonasoft Golden Gate Software Lumigent Red Gate Software Quest Software ApexSQL Idera Discussions about Books Discuss Programming Books Discuss XML Books Discuss T-SQL Books Discuss Data Warehousing Books Discuss DTS Books Discuss SQL Server 7.
What a pointer is, why links are different from pointers, how hierarchical and network databases worked, etc. What most draws me to Celko's ideas is that, both in this thread and his books, he backs his recommendations up with solid examples--not just hand waving and weasel words as masher2 did to a great degree. I know this is an old post, but I'm looking at same issue. sql server composite primary key I'm now convinced that what I once looked at as a specialty language SQL is in fact a rich and subtle tool that takes years to master. For example, a gardening book can contain one index for the common names of plants and another index for the scientific names because these are the two most common ways in which the readers find information. An interesting discussion on Surrogate vs. I think primary key PK would not be much of a concern here. Both examples are not correct as they have two T1 files for the same batch and group. This is behavior very difficult to achieve with a surrogate, but trivial with a natural key. If a large clustered index key is defined, any nonclustered indexes that are defined on the same table will be significantly larger because the nonclustered index entries contain the clustering key. Alternatively, a clustered index could be created on lname, fname last name, first namebecause employee records are often grouped and queried in this way rather than by employee ID. Thankfully, SQL Server has this information by using system DMVs dynamic management views along with the function.
