Difference Between Clustered and Non-Clustered Index
| CLUSTERED INDEX | NON-CLUSTERED INDEX |
|---|---|
| A clustered index is faster. | A non-clustered index is slower. |
| The clustered index requires less memory for operations. | A non-Clustered index requires more memory for operations. |
| In a clustered index, the clustered index is the main data. | In the Non-Clustered index, the index is the copy of data. |
| A table can have only one clustered index. | A table can have multiple non-clustered indexes. |
| The clustered index has the inherent ability to store data on the disk. | A non-Clustered index does not have the inherent ability to store data on the disk. |
| Clustered index store pointers to block not data. | The non-clustered index stores both the value and a pointer to the actual row that holds the data |
| In Clustered index leaf nodes are actual data itself. | In Non-Clustered index leaf nodes are not the actual data itself rather they only contain included columns. |
| In a Clustered index, Clustered key defines the order of data within a table. | In a Non-Clustered index, the index key defines the order of data within the index. |
| A Clustered index is a type of index in which table records are physically reordered to match the index. | A Non-Clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on the disk. |
| The size of The primary clustered index is large. | The size of the non-clustered index is compared relativelyThe composite is smaller. |
| Primary Keys of the table by default are clustered indexes. | The composite key when used with unique constraints of the table act as the non-clustered index. |
Difference Between Clustered and Non-Clustered Index
In SQL Server, indexing plays a crucial role in enhancing data retrieval efficiency. Indexes are disk-based structures linked to tables or views, aiding in quicker row retrieval by organizing data in a structured manner. Two primary types of indexes in SQL Server are Clustered and Non-Clustered Indexes.
An index is a disk-based structure linked to a table or view that facilitates quicker row retrieval. A table or view’s table or view’s columns are used to create keys in an index. These keys are kept in a structure (B-tree) that enables SQL Server to quickly and effectively locate the row or rows that correspond to the key values.