How do I obtain a Query Execution Plan in SQL Server?

Question

In Microsoft SQL Server how can I get a query execution plan for a query / stored procedure?

Answer 1

As I explained in this article, there are two execution plan types you can get when using SQL Server.

Estimated execution plan

The estimated execution plan is generated by the Optimizer without running the SQL query.

In order to get the estimated execution plan, you need to enable the SHOWPLAN_ALL setting prior to executing the query.

SET SHOWPLAN_ALL ON

Now, when executing the following SQL query:

SELECT p.id
FROM post p
WHERE EXISTS (
  SELECT 1
  FROM post_comment pc
  WHERE
    pc.post_id = p.id AND
    pc.review = 'Bingo'
)
ORDER BY p.title
OFFSET 20 ROWS
FETCH NEXT 10 ROWS ONLY

SQL Server will generate the following estimated execution plan:

| NodeId | Parent | LogicalOp            | EstimateRows | EstimateIO  | EstimateCPU | AvgRowSize | TotalSubtreeCost | EstimateExecutions |
|--------|--------|----------------------|--------------|-------------|-------------|------------|------------------|--------------------|
| 1      | 0      | NULL                 | 10           | NULL        | NULL        | NULL       | 0.03374284       | NULL               |
| 2      | 1      | Top                  | 10           | 0           | 3.00E-06    | 15         | 0.03374284       | 1                  |
| 4      | 2      | Distinct Sort        | 30           | 0.01126126  | 0.000504114 | 146        | 0.03373984       | 1                  |
| 5      | 4      | Inner Join           | 46.698       | 0           | 0.00017974  | 146        | 0.02197446       | 1                  |
| 6      | 5      | Clustered Index Scan | 43           | 0.004606482 | 0.0007543   | 31         | 0.005360782      | 1                  |
| 7      | 5      | Clustered Index Seek | 1            | 0.003125    | 0.0001581   | 146        | 0.0161733        | 43                 |

After running the query we are interested in getting the estimated execution plan, you need to disable the SHOWPLAN_ALL as, otherwise, the current database session will only generate estimated execution plan instead of executing the provided SQL queries.

SET SHOWPLAN_ALL OFF

SQL Server Management Studio estimated plan

In the SQL Server Management Studio application, you can easily get the estimated execution plan for any SQL query by hitting the CTRL+L key shortcut.

Actual execution plan

The actual SQL execution plan is generated by the Optimizer when running the SQL query. If the database table statistics are accurate, the actual plan should not differ significantly from the estimated one.

To get the actual execution plan on SQL Server, you need to enable the STATISTICS IO, TIME, PROFILE settings, as illustrated by the following SQL command:

SET STATISTICS IO, TIME, PROFILE ON

Now, when running the previous query, SQL Server is going to generate the following execution plan:

| Rows | Executes | NodeId | Parent | LogicalOp            | EstimateRows | EstimateIO  | EstimateCPU | AvgRowSize | TotalSubtreeCost |
|------|----------|--------|--------|----------------------|--------------|-------------|-------------|------------|------------------|
| 10   | 1        | 1      | 0      | NULL                 | 10           | NULL        | NULL        | NULL       | 0.03338978       |
| 10   | 1        | 2      | 1      | Top                  | 1.00E+01     | 0           | 3.00E-06    | 15         | 0.03338978       |
| 30   | 1        | 4      | 2      | Distinct Sort        | 30           | 0.01126126  | 0.000478783 | 146        | 0.03338679       |
| 41   | 1        | 5      | 4      | Inner Join           | 44.362       | 0           | 0.00017138  | 146        | 0.02164674       |
| 41   | 1        | 6      | 5      | Clustered Index Scan | 41           | 0.004606482 | 0.0007521   | 31         | 0.005358581      |
| 41   | 41       | 7      | 5      | Clustered Index Seek | 1            | 0.003125    | 0.0001581   | 146        | 0.0158571        |

SQL Server parse and compile time:
   CPU time = 8 ms, elapsed time = 8 ms.

(10 row(s) affected)
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'post'. Scan count 0, logical reads 116, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'post_comment'. Scan count 1, logical reads 5, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(6 row(s) affected)

SQL Server Execution Times:
   CPU time = 0 ms,  elapsed time = 1 ms.

After running the query we are interested in getting the actual execution plan, you need to disable the STATISTICS IO, TIME, PROFILE ON settings like this:

SET STATISTICS IO, TIME, PROFILE OFF

SQL Server Management Studio actual plan

In the SQL Server Management Studio application, you can easily get the estimated execution plan for any SQL query by hitting the CTRL+M key shortcut.

For more details about getting an execution plan when using SQL Server, check out this article.