I am trying to understand why is my query (update statement) causing clustered index update in the plan? Based on my clustered index (in the where clause), I am just updating columns in my table. What is the need for SQL Server to do clustered index update? I am not updating clustered key for SQL Server to reorganize/order the table according to clustered key, instead it has to update the columns or NC index on them wherein clustered key pointer to the NC rows will be the same (since I am not updating the clustered key). Can someone explain me why such behavior from SQL Server?

  • 4
    Look up the definition of a "Clustered Index".
    – pmbAustin
    Apr 12, 2015 at 23:34
  • 3
    The clustered index is the same as the table in SQL Server. A table without a clustered index is technically a heap.
    – Dan Guzman
    Apr 13, 2015 at 1:00

1 Answer 1


A clustered index stores all columns from the table, and is effectively the table's data source. Therefore, updating the table in any way will update the clustered index.

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