Does staging table have primary keys?
Staging Table has 2 primary keys defined for Unique Identifier.
Should primary key be clustered?
By default a primary keys gets to be the clustered index key too, but this is not a requirement. The primary key is a logical concept: is the key used in your data model to reference entities. The clustered index key is a physical concept: is the order in which you want the rows to be stored on disk.
What is the difference between a heap table and a clustered table How can we identify if the table is a heap table?
A heap is a table without a clustered index. One or more nonclustered indexes can be created on tables stored as a heap. Data is stored in the heap without specifying an order. To specify a permanent logical order for storing the rows, create a clustered index on the table, so that the table is not a heap.
What is the difference between heap table and temporary table?
As you quoted yourself, temporary tables are only valid during the session while heap tables exist in memory. So a heap table can exist for a long time if you do not restart your Database. For temporary tables you need a special privilege (create temporary table) while heap tables are just another storage engine.
What happens when a clustered table is created on a heap?
But if your table is either a heap or a clustered table and there are a lot of INSERTs, UPDATEs and DELETEs the data pages can become fragmented. This results in wasted space as well as additional data pages to read to satisfy queries. When a table is created as a heap, SQL Server does not force where the new data pages are written.
Why do clustered tables have a clustered index?
So based on this, most of your tables are going to have a clustered index, because of the primary key, but if you do not specify a primary key or build a clustered index the data will be stored as a heap. Keeping table and index fragmentation under control is a key process to maintain optimum performance out of your database.
What happens when you delete a heap table in SQL Server?
Also, when you delete data from a heap SQL Server does not always deallocate the space for the free pages. With a clustered index, depending on the index key, new records may be written to existing pages where free space exists or there may be need to split a page into multiple pages in order to insert the new data.
How many heap structures are there in a table?
Heap Structures. By default, a heap has a single partition. When a heap has multiple partitions, each partition has a heap structure that contains the data for that specific partition. For example, if a heap has four partitions, there are four heap structures; one in each partition.