clustered-index

The goal of using a sequential guid is so you can use clustered indexes without the high levels of fragmentation that would normally exist in a clustered index if it was a regular guid, correct? Yes, you are correct. First to clarify, a primary key and clustered index are 2 separate and distinct things, i.e. one is not coupled to the other (PKs can be nonclustered, clustered indexes can be non-PKs). That given, I think you're asking more "Should a Sequential GUID be used as a clustered index". That's a loaded question, but Kimberly Tripp has discussed this probably the best of anyone I've seen

From EF6.1, we have a way of specifying a clustered index on a property public class Person { [Index(IsClustered = true, IsUnique = true)] public long UserName { get; set; } } But this Index attribute does not seem to be in EF Core right now? In EF Core how do you achieve this? From the current EF Core documentation - Indexes section: Data Annotations Indexes can not be created using data annotations. But for sure you can specify that via Fluent API (note the extension methods having ForSqlServer prefix which seem to denote SqlServer specific features): modelBuilder.Entity<Person>() .HasIndex

If you have a table with a clustered index on the Primary Key (int), is it redundant and bad to have one (ore more) non-clustered indexes that include that primary key column as one of the columns in the non-clustered index? Actually there could be valid reasons to create a non-clustered index identical with the clustered one. The reason is that clustered indexes carry the baggage of the row data and this can make very poor row density. Ie. you can have 2-3 rows per page due to wide fields that are not in the clustered key, but the clustered index key is only, say, 20 bytes. Having a non

When a table has a clustered index in SQL Server does that mean that all indexed queries will go via the clustered index? For example if I have a table with a single non-clustered index (indexing one column) and search for a row via that column it will do Index Seek -> RID -> Data row lookup -> Result But if I add a clustered index on a different column then the same query will do the following Index Seek -> Extract clustering key -> Clustered index seek -> Results This implies to me that the non-clustered index no longer 'terminates' with a RID at the leaf but with a clustering key of the

I have a table which has a clustered index on two columns - the primary key for the table. It is defined as follows: ALTER TABLE Table ADD CONSTRAINT [PK_Table] PRIMARY KEY CLUSTERED ( [ColA] ASC, [ColB] ASC )WITH (SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF) ON [PRIMARY] I want to remove this clustered index PK and add a clustered index like follows and add a primary key constraint using a non-clustered index, also shown below. CREATE CLUSTERED INDEX [IX_Clustered] ON [Table] ( [ColC] ASC, [ColA] ASC, [ColD] ASC, [ColE] ASC, [ColF] ASC, [ColG] ASC )WITH (PAD_INDEX = ON,

Is it possible to write a query that returns all tables that have clustered indexes that are not based on an identity key? How about this: SELECT TableName = t.name, ClusteredIndexName = i.name, ColumnName = c.Name FROM sys.tables t INNER JOIN sys.indexes i ON t.object_id = i.object_id INNER JOIN sys.index_columns ic ON i.index_id = ic.index_id AND i.object_id = ic.object_id INNER JOIN sys.columns c ON ic.column_id = c.column_id AND ic.object_id = c.object_id WHERE i.index_id = 1 -- clustered index AND c.is_identity = 0 AND EXISTS (SELECT * FROM sys.columns c2 WHERE ic.object_id = c2.object_id

I have a SQLServer table that stores employee details, the column ID is of GUID type while the column EmployeeNumber of INT type. Most of the time I will be dealing with EmployeeNumber while doing joins and select criteria's. My question is, whether is it sensible to assign PrimaryKey to ID column while ClusteredIndex to EmployeeNumber? The ideal clustered index key is: Sequential Selective (no dupes, unique for each record) Narrow Used in Queries In general it is a very bad idea to use a GUID as a clustered index key, since it leads to mucho fragmentation as rows are added. EDIT FOR CLARITY: