Create Statistics

You can create query optimization statistics on one or more columns of a table or indexed view in SQL Server 2012 by using SQL Server Management Studio or Transact-SQL. For most queries, the query optimizer already generates the necessary statistics for a high-quality query plan; in a few cases, you need to create additional statistics.

In This Topic

• Before you begin:

  Limitations and Restrictions

  Security

• To create statistics, using:

  SQL Server Management Studio

  Transact-SQL

Before You Begin

Limitations and Restrictions

• Before creating statistics with the CREATE STATISTICS statement, verify that the AUTO_CREATE_STATISTICS option is set at the database level. This will ensure that the query optimizer continues to routinely create single-column statistics for query predicate columns.

• You can list up to 32 columns per statistics object.

• You cannot drop, rename, or alter the definition of a table column that is defined in a filtered statistics predicate.

Security

Permissions

Requires that the user be the table or indexed view owner, or a member of one of the following roles: sysadmin fixed server role, db_owner fixed database role, or the db_ddladmin fixed database role.

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Using SQL Server Management Studio

To create statistics

1. In Object Explorer, click the plus sign to expand the database in which you want to create a new statistic.

2. Click the plus sign to expand the Tables folder.

3. Click the plus sign to expand the table in which you want to create a new statistic.

4. Right-click the Statistics folder and select New Statistics….

   The following properties show on the General page in the New Statistics on Table table_name dialog box.

   • Table Name
     Displays the name of the table described by the statistics.

   • Statistics Name
     Displays the name of the database object where the statistics are stored.

   • Statistics Columns
     This grid shows the columns described by this set of statistics. All values in the grid are read-only.

   • Name
     Displays the name of the column described by the statistics. This can be a single column or a combination of columns in a single table.

   • Data Type
     Indicates the data type of the columns described by the statistics.

   • Size
     Displays the size of the data type for each column.

   • Identity
     Indicates an identity column when it is checked.

   • Allow Nulls
     Indicates whether the column accepts NULL values.

   • Add
     Add additional columns from the table to the statistics grid.

   • Remove
     Remove the selected column from the statistics grid.

   • Move Up
     Move the selected column to an earlier location in the statistics grid. The location in the grid can substantially impact the usefulness of the statistics.

   • Move Down
     Move the selected column to a later location in the statistics grid.

   • Statistics for these columns were last updated:
     Indicates how old the statistics are. Statistics are more valuable when they are current. Update statistics after large changes to the data or after adding atypical data. Statistics for tables that have a consistent distribution of data need to be updated less frequently.

   • Update statistics for these columns
     Check to update the statistics when the dialog box is closed.

   The following property shows on the Filter page in the New Statistics on Table table_name dialog box.

   • Filter Expression
     Defines which data rows to include in the filtered statistics. For example, Production.ProductSubcategoryID IN ( 1,2,3 )

5. In the New Statistics on Table table_name dialog box, on the General page, click Add.

   The following properties show in the Select Columns dialog box. This information is read-only.

   • Name
     Displays the name of the column described by the statistics. This can be a single column or a combination of columns in a single table.

   • Data Type
     Indicates the data type of the columns described by the statistics.

   • Size
     Displays the size of the data type for each column.

   • Identity
     Indicates an identity column when checked.

   • Allow NULLs
     Indicates whether the column accepts NULL values.

6. In the Select Columns dialog box, select the check box or check boxes of each column for which you want to create a statistic and then click OK.

7. In the New Statistics on Table table_name dialog box, click OK.

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Using Transact-SQL

To create statistics

1. In Object Explorer, connect to an instance of Database Engine.

2. On the Standard bar, click New Query.

3. Copy and paste the following example into the query window and click Execute.

   USE AdventureWorks2012; 
   GO
   -- Create new statistic object called ContactMail1
   -- on the BusinessEntityID and EmailPromotion columns in the Person.Person table. 
   
   CREATE STATISTICS ContactMail1
       ON Person.Person (BusinessEntityID, EmailPromotion); 
   GO
   

4. The statistic created above potentially improves the results for the following query.

   USE AdventureWorks2012; 
   GO
   SELECT LastName, FirstName
   FROM Person.Person
   WHERE EmailPromotion = 2
   ORDER BY LastName, FirstName; 
   GO
   

For more information, see CREATE STATISTICS (Transact-SQL).

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