解释执行计划可能会非常详细，并占用大量阅读时间，但总的来说，如果你在查询之前使用'explain'，它应该会给你很多信息，包括哪些部分首先执行等等。 如果你想了解更多关于这方面的细节，我写了一篇关于这方面的小博客，它也会给你指明正确的裁判。 https://medium.com/swlh/jetbrains-datagrip-explain-plan-ac406772c470

查询计划可以通过query_post_execution_showplan事件从扩展事件会话中获得。下面是一个XEvent会话示例:

/*
    Generated via "Query Detail Tracking" template.
*/
CREATE EVENT SESSION [GetExecutionPlan] ON SERVER 
ADD EVENT sqlserver.query_post_execution_showplan(
    ACTION(package0.event_sequence,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)),

/* Remove any of the following events (or include additional events) as desired. */
ADD EVENT sqlserver.error_reported(
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))),
ADD EVENT sqlserver.module_end(SET collect_statement=(1)
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))),
ADD EVENT sqlserver.rpc_completed(
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))),
ADD EVENT sqlserver.sp_statement_completed(SET collect_object_name=(1)
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))),
ADD EVENT sqlserver.sql_batch_completed(
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))),
ADD EVENT sqlserver.sql_statement_completed(
    ACTION(package0.event_sequence,sqlserver.client_app_name,sqlserver.database_id,sqlserver.plan_handle,sqlserver.query_hash,sqlserver.query_plan_hash,sqlserver.session_id,sqlserver.sql_text,sqlserver.tsql_frame,sqlserver.tsql_stack)
    WHERE ([package0].[greater_than_uint64]([sqlserver].[database_id],(4)) AND [package0].[equal_boolean]([sqlserver].[is_system],(0)))) 
ADD TARGET package0.ring_buffer
WITH (MAX_MEMORY=4096 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=30 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=NONE,TRACK_CAUSALITY=ON,STARTUP_STATE=OFF)
GO

创建会话后，(在SSMS中)转到对象资源管理器并深入到管理|扩展事件|会话。右键单击“GetExecutionPlan”会话并启动它。再次右键选择“观看实时数据”。

接下来，打开一个新的查询窗口并运行一个或多个查询。以下是AdventureWorks的一个例子:

USE AdventureWorks;
GO

SELECT p.Name AS ProductName, 
    NonDiscountSales = (OrderQty * UnitPrice),
    Discounts = ((OrderQty * UnitPrice) * UnitPriceDiscount)
FROM Production.Product AS p 
INNER JOIN Sales.SalesOrderDetail AS sod
    ON p.ProductID = sod.ProductID 
ORDER BY ProductName DESC;
GO

过一会儿，您应该在“GetExecutionPlan: Live Data”选项卡中看到一些结果。单击网格中的query_post_execution_showplan事件之一，然后单击网格下面的“Query Plan”选项卡。它应该看起来像这样:

编辑:XEvent代码和屏幕截图是从SQL/SSMS 2012 w/ SP2生成的。如果您使用的是SQL 2008/R2，则可以调整脚本以使其运行。但那个版本没有GUI，所以你需要提取showplan XML，保存为*。并在SSMS中打开。这是麻烦的。XEvents在SQL 2005或更早的版本中并不存在。所以，如果你没有使用SQL 2012或更高版本，我强烈建议你使用这里发布的其他答案之一。

从SQL Server 2016+开始，引入了查询存储功能来监控性能。它提供了对查询计划选择和性能的洞察。 它并不是跟踪或扩展事件的完全替代，但随着它从一个版本到另一个版本的发展，我们可能会在SQL Server的未来版本中得到一个功能齐全的查询存储。 查询存储的主要流程

SQL Server existing components interact with query store by utilising Query Store Manager. Query Store Manager determines which Store should be used and then passes execution to that store (Plan or Runtime Stats or Query Wait Stats) Plan Store - Persisting the execution plan information Runtime Stats Store - Persisting the execution statistics information Query Wait Stats Store - Persisting wait statistics information. Plan, Runtime Stats and Wait store uses Query Store as an extension to SQL Server.

Enabling the Query Store: Query Store works at the database level on the server. Query Store is not active for new databases by default. You cannot enable the query store for the master or tempdb database. Available DMV sys.database_query_store_options (Transact-SQL) Collect Information in the Query Store: We collect all the available information from the three stores using Query Store DMV (Data Management Views). Query Plan Store: Persisting the execution plan information and it is accountable for capturing all information that is related to query compilation. sys.query_store_query (Transact-SQL) sys.query_store_plan (Transact-SQL) sys.query_store_query_text (Transact-SQL) Runtime Stats Store: Persisting the execution statistics information and it is probably the most frequently updated store. These statistics represent query execution data. sys.query_store_runtime_stats (Transact-SQL) Query Wait Stats Store: Persisting and capturing wait statistics information. sys.query_store_wait_stats (Transact-SQL)

注意:查询等待统计数据存储仅在SQL Server 2017+中可用

除了已经发布的综合答案之外，有时能够以编程方式访问执行计划以提取信息也是有用的。下面是示例代码。

DECLARE @TraceID INT
EXEC StartCapture @@SPID, @TraceID OUTPUT
EXEC sp_help 'sys.objects' /*<-- Call your stored proc of interest here.*/
EXEC StopCapture @TraceID

StartCapture定义

CREATE PROCEDURE StartCapture
@Spid INT,
@TraceID INT OUTPUT
AS
DECLARE @maxfilesize BIGINT = 5
DECLARE @filepath NVARCHAR(200) = N'C:\trace_' + LEFT(NEWID(),36)

EXEC sp_trace_create @TraceID OUTPUT, 0, @filepath, @maxfilesize, NULL 

exec sp_trace_setevent @TraceID, 122, 1, 1
exec sp_trace_setevent @TraceID, 122, 22, 1
exec sp_trace_setevent @TraceID, 122, 34, 1
exec sp_trace_setevent @TraceID, 122, 51, 1
exec sp_trace_setevent @TraceID, 122, 12, 1
-- filter for spid
EXEC sp_trace_setfilter @TraceID, 12, 0, 0, @Spid
-- start the trace
EXEC sp_trace_setstatus @TraceID, 1

停止捕获定义

CREATE  PROCEDURE StopCapture
@TraceID INT
AS
WITH  XMLNAMESPACES ('http://schemas.microsoft.com/sqlserver/2004/07/showplan' as sql), 
      CTE
     as (SELECT CAST(TextData AS VARCHAR(MAX)) AS TextData,
                ObjectID,
                ObjectName,
                EventSequence,
                /*costs accumulate up the tree so the MAX should be the root*/
                MAX(EstimatedTotalSubtreeCost) AS EstimatedTotalSubtreeCost
         FROM   fn_trace_getinfo(@TraceID) fn
                CROSS APPLY fn_trace_gettable(CAST(value AS NVARCHAR(200)), 1)
                CROSS APPLY (SELECT CAST(TextData AS XML) AS xPlan) x
                CROSS APPLY (SELECT T.relop.value('@EstimatedTotalSubtreeCost',
                                            'float') AS EstimatedTotalSubtreeCost
                             FROM   xPlan.nodes('//sql:RelOp') T(relop)) ca
         WHERE  property = 2
                AND TextData IS NOT NULL
                AND ObjectName not in ( 'StopCapture', 'fn_trace_getinfo' )
         GROUP  BY CAST(TextData AS VARCHAR(MAX)),
                   ObjectID,
                   ObjectName,
                   EventSequence)
SELECT ObjectName,
       SUM(EstimatedTotalSubtreeCost) AS EstimatedTotalSubtreeCost
FROM   CTE
GROUP  BY ObjectID,
          ObjectName  

-- Stop the trace
EXEC sp_trace_setstatus @TraceID, 0
-- Close and delete the trace
EXEC sp_trace_setstatus @TraceID, 2
GO

除了前面所说的，还有一件重要的事情需要知道。

Query plans are often too complex to be represented by the built-in XML column type which has a limitation of 127 levels of nested elements. That is one of the reasons why sys.dm_exec_query_plan may return NULL or even throw an error in earlier MS SQL versions, so generally it's safer to use sys.dm_exec_text_query_plan instead. The latter also has a useful bonus feature of selecting a plan for a particular statement rather than the whole batch. Here's how you use it to view plans for currently running statements:

SELECT p.query_plan
FROM sys.dm_exec_requests AS r
OUTER APPLY sys.dm_exec_text_query_plan(
                r.plan_handle,
                r.statement_start_offset,
                r.statement_end_offset) AS p

然而，与XML列相比，结果表中的文本列不是很方便。为了能够单击要在单独的选项卡中作为图表打开的结果，而不必将其内容保存到文件中，您可以使用一个小技巧(记住您不能只使用CAST(…AS XML))，尽管这将只适用于单行:

SELECT Tag = 1, Parent = NULL, [ShowPlanXML!1!!XMLTEXT] = query_plan
FROM sys.dm_exec_text_query_plan(
                -- set these variables or copy values
                -- from the results of the above query
                @plan_handle,
                @statement_start_offset,
                @statement_end_offset)
FOR XML EXPLICIT

除了前面回答中描述的方法外，您还可以使用免费的执行计划查看器和查询优化工具ApexSQL plan(我最近碰到了它)。

您可以将ApexSQL计划安装并集成到SQL Server Management Studio中，因此可以直接从SSMS查看执行计划。

在“ApexSQL计划”中查看估计的执行计划

单击SSMS中的新建查询按钮，并将查询文本粘贴到查询文本窗口中。右击并从上下文菜单中选择“Display Estimated Execution Plan”选项。

执行计划图将显示在结果部分的execution plan选项卡中。接下来右键单击执行计划，在上下文菜单中选择“在ApexSQL计划中打开”选项。

预估执行计划将在ApexSQL plan中打开，可以对其进行分析以进行查询优化。

在“ApexSQL计划”中查看实际执行计划

要查看查询的实际执行计划，从前面提到的第二步继续，但是现在，一旦估计计划显示出来，在ApexSQL计划的主带栏中单击“实际”按钮。

一旦点击“实际”按钮，实际执行计划将显示详细的成本参数预览以及其他执行计划数据。

点击此链接可以找到有关查看执行计划的更多信息。