Index Seek vs Index Scan in SQL Server

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Answer 1

Here is the text showplan (slightly edited for brevity) for this query using a scan:

|–Table Scan(OBJECT:([ORDERS]), WHERE:([ORDERKEY]=(2)))

The following figure illustrates the scan:

Here is the text showplan for the same query using a seek:

 |–Index Seek(OBJECT:([ORDERS].[OKEY_IDX]), SEEK:([ORDERKEY]=(2)) ORDERED FORWARD)

have a look on this SQL Server Plans : difference between Index Scan / Index Seek