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When to use index scan instead of index seek?
From the previous steps we know that with more than 38 rows the optimiser will opt for a clustered index scan over an index seek, so since the best guess for the number of rows is higher than this, the plan for an unknown variable is a clustered index scan.
Which is more efficient index scan or index scan?
Scan count 100, logical reads 409, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. For that query index seeks can be viewed as more efficient than an index scan. Note that the outer table has 100 rows so 100 seeks were done.
Why does SQL Server not use index scan?
If your query is returning too many rows, a high percentage of the total rows in the table, SQL Server will not use the index. This happens because the cost of the key lookup for each row can be bigger than the cost of an entire scan.
Which is better, a scan or a seek?
There is much, much more to it than a simple “scan vs seek” question. SQL can do both well, and badly, depending on other factors. One seek might be executed 900 times returning one row each time, where a scan might return all 900 rows in one visit. The scan is better in that scenario.
Is it possible to force SQL to seek an index?
It is possible to force SQL to seek an index by using the FORCESEEK query hint, but please use this with caution, as generally, providing you keep everything weel maintained, SQL is pretty good at deciding what the most efficient plan will be!! In Short: You do not have filter on LocationCache, the whole table content should be returned.
Which is more efficient index scan or index predicate?
Index Scan: Since a scan touches every row in the table whether or not it qualifies, the cost is proportional to the total number of rows in the table. Thus, a scan is an efficient strategy if the table is small or if most of the rows qualify for the predicate.
Index Seek: Since a seek only touches rows that qualify and pages that contain these qualifying rows, the cost is proportional to the number of qualifying rows and pages rather than to the total number of rows in the table.