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Do indexes affect inserts?
The number of indexes on a table is the most dominant factor for insert performance. The more indexes a table has, the slower the execution becomes. The insert statement is the only operation that cannot directly benefit from indexing because it has no where clause. Adding a new row to a table involves several steps.
Should I create index before or after insert?
You should create an index for a table after inserting or loading data (via SQL*Loader or Import) into the table. It is more efficient to insert rows of data into a table that has no indexes and then create the indexes for subsequent access.
How indexes affect insert update and delete performance?
If you update a table, the system has to maintain those indexes that are on the columns being updated. So having a lot of indexes can speed up select statements, but slow down inserts, updates, and deletes.
How to insert into a table with a clustered index?
You can optimize an INSERT statement into a table with a clustered index, by using a minimally-logged INSERT, but that’s out of scope for this question. Updated 2011-11-02: As Mark Smith has shown, INSERT s into a table with a clustered index might not always require to be sorted — the ORDER BY clause is also redundant in that case, though.
When to use clustered index key in SQL Server?
One notable example is when inserting a large number of rows into a table with a newsequentialid clustered index key. In versions of SQL Server prior to Denali SQL Server adds an unnecessary and potentially expensive sort operation. This can be avoided by
How to insert 100 rows in SQL Server?
In versions of SQL Server prior to Denali SQL Server adds an unnecessary and potentially expensive sort operation. This can be avoided by SQL Server will then estimate that 100 rows will be inserted irrespective of the size of Bar which is below the threshold at which a sort is added to the plan.
When to underestimate the row count in SQL Server?
Conversely sometimes you might want to force SQL Server to underestimate the row count when you know the data is already pre-sorted and wish to avoid an unnecessary sort. One notable example is when inserting a large number of rows into a table with a newsequentialid clustered index key.