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sys.dm_db_missing_index_columns

Updated: April 2, 2011

This topic is OBSOLETE. You can find the most current version in the SQL 14 Transact-SQL Reference.

ImportantImportant
This topic is not maintained. For the current version, see sys.dm_db_missing_index_columns.

Returns information about database table columns that are missing an index, excluding spatial indexes. sys.dm_db_missing_index_columns is a dynamic management function.


sys.dm_db_missing_index_columns(index_handle)

index_handle
An integer that uniquely identifies a missing index. It can be obtained from the following dynamic management objects:

About the Missing Indexes Feature

sys.dm_db_missing_index_groups

 

Column name Data type Description

column_id

int

ID of the column.

column_name

sysname

Name of the table column.

column_usage

varchar(20)

How the column is used by the query. Possible values are:

 

Value Description

EQUALITY

Column contributes to a predicate that expresses equality, of the form:

table.column =constant_value

INEQUALITY

Column contributes to a predicate that expresses inequality, for example, a predicate of the form:

table.column > constant_value

Any comparison operator other than "=" expresses inequality.

INCLUDE

Column is not used to evaluate a predicate, but is used for another reason, for example, to cover a query.

Information returned by sys.dm_db_missing_index_columns is updated when a query is optimized by the query optimizer, and is not persisted. Missing index information is kept only until SQL Server is restarted. Database administrators should periodically make backup copies of the missing index information if they want to keep it after server recycling.

Transaction Consistency

If a transaction creates or drops a table, the rows containing missing index information about the dropped objects are removed from this dynamic management object, preserving transaction consistency.

Requires VIEW DATABASE STATE permission on server. Cannot be queried from the master database. For more information, see Dynamic Management Objects.

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