SET Statements for SQLServer

SET
SHOWPLAN_ALL { ON | OFF }

  • It will not
    execute the TSQL statements.

  • It cannot
    be specified inside a stored procedure,must be the only statements in a
    batch.

  • Returns
    information as a set of rows that form a hierarchical tree representing the
    steps taken by the SQL Server query processor as it executes each statement.
    Each statement reflected in the output contains a single row with the text of
    the statement, followed by several rows with the details of the execution
    steps.

SET
SHOWPLAN_ALL ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
SHOWPLAN_ALL OFF;
GO

All
the information in the resultset are estimated, no any actual statistics
information.

SET
SHOWPLAN_XML { ON | OFF }

  • It will not
    execute the TSQL statements.

  • It will
    return detailed information about how the statements are going to be executed
    in XML.

SET
SHOWPLAN_XML ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
SHOWPLAN_XML OFF;
GO

SET
SHOWPLAN_TEXT { ON | OFF }

  • It will not
    execute the TSQL statements.

  • It cannot be
    specified inside a stored procedure,must be the only statements in a
    batch.

  • Returns
    information as a set of rows that form a hierarchical tree representing the
    steps taken by the SQL Server query processor as it executes each statement.
    Each statement reflected in the output
    contains a single row with the text of the statement, followed by
    several rows with the details of the execution steps. The table shows the
    column that the output contains.

  • SET
    SHOWPLAN_TEXT is intended to return readable output for Microsoft Win32
    command prompt applications such as
    the osql utility. SET SHOWPLAN_ALL
    returns more detailed output intended to be used with programs designed to
    handle its output.

SET
SHOWPLAN_TEXT ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
SHOWPLAN_TEXT OFF;
GO

SET
STATISTICS PROFILE { ON | OFF }

  • It
    will execute the TSQL statements.

  • Returns
    information as a set of rows that form a hierarchical tree representing the
    steps taken by the SQL Server query processor as it executes each statement.
    Each statement reflected in the output contains a single row with the text of
    the statement, followed by several rows with the details of the execution
    steps.

  • While
    compare with SHOWPLAN_ALL, it has two additional column
    Rows,Executes.

SET
statistics profile ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
statistics profile OFF;
GO


SET
STATISTICS XML { ON | OFF }

  • It will
    execute the TSQL statements.

  • It will
    generate detailed information about how the statements were executed in
    XML.

  • SET
    STATISTICS XML need not be the only statement in a batch.

  • SET
    STATISTICS XML returns output as nvarchar(max) for applications, such as
    the sqlcmd utility, where the XML output is
    subsequently used by other tools to display and process the query plan
    information. The xml comply with below xsd file \Microsoft SQL Server\100\Tools\Binn\schemas\sqlserver\2004\07\showplan\showplanxml.xsd

  • SET
    STATISTICS PROFILE and SET STATISTICS XML are counterparts of each other. The
    former produces textual output; the latter produces XML output. In
    future versions of SQL Server, new query execution plan information will only
    be displayed through the SET STATISTICS XML statement, not the SET STATISTICS
    PROFILE statement.

  • If Include Actual Execution Plan is selected in SQL
    Server Management Studio, this SET option does not produce XML Showplan
    output. Clear the Include Actual Execution
    Plan button before using this SET
    option.

SET
STATISTICS XML ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
STATISTICS XML OFF;
GO

SET
STATISTICS TIME { ON | OFF }

  • When SET
    STATISTICS TIME is ON, the time statistics for a statement are displayed. When
    OFF, the time statistics are not displayed.

  • The setting of SET
    STATISTICS TIME is set at execute or run time and not at parse
    time.

  • Microsoft SQL
    Server is unable to provide accurate statistics in fiber mode, which is
    activated when you enable the lightweight
    pooling     configuration option.

  • The cpu column
    in the sysprocesses table is only updated when a
    query executes with SET STATISTICS TIME ON. When SET STATISTICS TIME is
    OFF, 0 is returned.

  • ON and OFF
    settings also affect the CPU column in the Process Info View for Current
    Activity in SQL Server Management Studio.

SET
STATISTICS TIME ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
STATISTICS TIME OFF;
GO

SET
STATISTICS IO { ON | OFF }

  • When
    STATISTICS IO is ON, statistical information is displayed. When OFF, the
    information is not displayed.

  • After this
    option is set ON, all subsequent Transact-SQL statements return the
    statistical information until the option is set to OFF.

  • When
    Transact-SQL statements retrieve LOB columns, some LOB retrieval operations
    might require traversing the LOB tree multiple times. This may cause SET
    STATISTICS IO to report higher than expected logical reads.





























  • Output
    item

    Meaning

    Table

    Name
    of the table.

    Scan
    count

    Number
    of seeks/scans started after reaching the leaf level in any direction to
    retrieve all the values to construct the final dataset for the
    output.

    • Scan
      count is 0 if the index used is a unique index or clustered index on a
      primary key and you are seeking for only one value. For
      example WHERE Primary_Key_Column =
      <value>.

    • Scant
      count is 1 when you are searching for one value using a non-unique
      clustered index which is defined on a non-primary key column. This is
      done to check for duplicate values for the key value that you are
      searching for. For example WHERE
      Clustered_Index_Key_Column = <value>.

    • Scan
      count is N when N is the number of different seek/scan started towards
      the left or right side at the leaf level after locating a key value
      using the index key.

    logical
    reads

    Number
    of pages read from the data cache.

    physical
    reads

    Number
    of pages read from disk.

    read-ahead
    reads

    Number
    of pages placed into the cache for the query.

    lob
    logical reads

    Number
    of text, ntext, image, or
    large value type (varchar(max), nvarchar(max), varbinary(max)) pages read from the data
    cache.

    lob
    physical reads

    Number
    of text, ntext, image or large value type pages read from
    disk.

    lob
    read-ahead reads

    Number
    of text, ntext, image or large value type pages placed into
    the cache for the query.

SET
STATISTICS IO ON;
GO
SELECT
BusinessEntityID, JobTitle
FROM
HumanResources.Employee
WHERE
JobTitle LIKE ‘Production%‘;
GO
SET
STATISTICS IO OFF;
GO

SET
FORCEPLAN { ON | OFF }

  • When
    FORCEPLAN is set to ON, the SQL Server query optimizer processes a join in the
    same order as the tables appear in the FROM clause of a query.
    In addition, setting FORCEPLAN to ON forces the use of a nested loop join
    unless other types of joins are required to construct a plan for the query, or
    they are requested with join hints or query hints.

  • SET
    FORCEPLAN essentially overrides the logic used by the query optimizer to
    process a Transact-SQL SELECT statement. The data returned by the SELECT
    statement is the same regardless of this setting. The only difference is the
    way in which SQL Server processes the tables to satisfy the query.Query
    optimizer hints can also be used in queries to affect how SQL Server processes
    the SELECT statement.
USE AdventureWorks2012;

GO

-- Make sure FORCEPLAN is set to OFF.

SET SHOWPLAN_TEXT OFF;

GO

SET FORCEPLAN OFF;

GO

SET SHOWPLAN_TEXT ON;

GO

-- Example where the query plan is not forced.

SELECT p.LastName, p.FirstName, v.Name

FROM Person.Person AS p

   INNER JOIN HumanResources.Employee AS e

   ON e.BusinessEntityID = p.BusinessEntityID

   INNER JOIN Purchasing.PurchaseOrderHeader AS poh

   ON e.BusinessEntityID = poh.EmployeeID

   INNER JOIN Purchasing.Vendor AS v

   ON poh.VendorID = v.BusinessEntityID;

GO

-- SET FORCEPLAN to ON.

SET SHOWPLAN_TEXT OFF;

GO

SET FORCEPLAN ON;

GO

SET SHOWPLAN_TEXT ON;

GO

-- Reexecute inner join to see the effect of SET FORCEPLAN ON.

SELECT p.LastName, p.FirstName, v.Name

FROM Person.Person AS p

   INNER JOIN HumanResources.Employee AS e

   ON e.BusinessEntityID = p.BusinessEntityID

   INNER JOIN Purchasing.PurchaseOrderHeader AS poh

   ON e.BusinessEntityID = poh.EmployeeID

   INNER JOIN Purchasing.Vendor AS v

   ON poh.VendorID = v.BusinessEntityID;

GO

SET SHOWPLAN_TEXT OFF;

GO

SET FORCEPLAN OFF;

GO



DBCC

DROPCLEANBUFFERS 清除数据缓存
DBCC FREEPROCCACHE  清除执行计划缓存


REFERENCES


SET

SHOWPLAN_XML
http://technet.microsoft.com/en-us/library/ms187757.aspx


SET

SHOWPLAN_TEXT


http://technet.microsoft.com/en-us/library/ms176058.aspx


SET

SHOWPLAN_ALL


http://technet.microsoft.com/en-us/library/ms187735.aspx


SET

STATISTICS PROFILE


http://technet.microsoft.com/en-us/library/ms188752.aspx


SET

STATISTICS XML
http://technet.microsoft.com/en-us/library/ms176107.aspx


SET

STATISTICS TIME


http://technet.microsoft.com/en-us/library/ms190287.aspx


SET

STATISTICS IO


http://technet.microsoft.com/en-us/library/ms184361.aspx


SET

FORCEPLAN


http://technet.microsoft.com/en-us/library/ms188344.aspx


SET

Statements (Transact-SQL)


http://msdn.microsoft.com/en-us/library/ms190356.aspx


SET Statements for SQLServer,码迷,mamicode.com
				


				
时间： 2024-12-28 18:13:14 

		


		


	

	
	

		


		
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