Learn T-SQL Querying

Table Scan

The Table Scan operator represents a scan operation on a heap. A table scan is a non-blocking operator that reads every page of the object and scans them for the desired rows. As illustrated in the preceding screenshot, a heap does not have any order or structure, so the rows will be output in a random order.

Here is an example of a query executed in the AdventureWorks sample database with a Table Scan operator:

SELECT * FROM DatabaseLog;

The query generates the following execution plan:

While a table scan may generate a large amount of I/O depending on the size of the table, the operator itself does not require a large amount of ...