Use these formulas for clustered and nonclustered indexes on data-only-length tables.
Index rows containing variable-length columns require more overhead than index rows containing only fixed-length values.
Use this formula if the index contains only fixed-length keys defined as NOT NULL:
9 |
(Overhead) |
|
+ |
Sum of fixed-length keys |
|
Size of index row |
Use this formula if the index contains any variable-length keys or columns that allow null values:
Formula |
Example |
|||
|---|---|---|---|---|
9 |
(Overhead) |
9 |
||
+ |
Sum of length of fixed-length keys |
+ |
4 |
|
+ |
Sum of length of variable-length keys |
+ |
20 |
|
+ |
Number of variable-length keys * 2 |
+ |
2 |
|
Size of index row |
35 |
|||
