sys.dm_db_missing_index_details (Transact-SQL)


Updated: June 10, 2016

THIS TOPIC APPLIES TO:yesSQL Server (starting with 2008)yesAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Returns detailed information about missing indexes, excluding spatial indexes.

In Azure SQL Database, dynamic management views cannot expose information that would impact database containment or expose information about other databases the user has access to. To avoid exposing this information, every row that contains data that doesn’t belong to the connected tenant is filtered out.

Column nameData typeDescription
index_handleintIdentifies a particular missing index. The identifier is unique across the server. index_handle is the key of this table.
database_idsmallintIdentifies the database where the table with the missing index resides.
object_idintIdentifies the table where the index is missing.
equality_columnsnvarchar(4000)Comma-separated list of columns that contribute to equality predicates of the form:

 table.column =constant_value
inequality_columnsnvarchar(4000)Comma-separated list of columns that contribute to inequality predicates, for example, predicates of the form:

 table.column > constant_value

Any comparison operator other than "=" expresses inequality.
included_columnsnvarchar(4000)Comma-separated list of columns needed as covering columns for the query. For more information about covering or included columns, see Create Indexes with Included Columns.

For memory-optimized indexes (both hash and memory-optimized nonclustered), ignore included_columns. All columns of the table are included in every memory-optimized index.
statementnvarchar(4000)Name of the table where the index is missing.

Information returned by sys.dm_db_missing_index_details 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.

To determine which missing index groups a particular missing index is part of, you can query the sys.dm_db_missing_index_groups dynamic management view by equijoining it with sys.dm_db_missing_index_details based on the index_handle column.

To convert the information returned by sys.dm_db_missing_index_details into a CREATE INDEX statement for both memory-optimized and disk-based indexes, equality columns should be put before the inequality columns, and together they should make the key of the index. Included columns should be added to the CREATE INDEX statement using the INCLUDE clause. To determine an effective order for the equality columns, order them based on their selectivity: list the most selective columns first (leftmost in the column list).

For more information about memory-optimized indexes, see Indexes for Memory-Optimized Tables.

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.

Users must be granted the VIEW SERVER STATE permission or any permission that implies the VIEW SERVER STATE permission to query this dynamic management view.

sys.dm_db_missing_index_columns (Transact-SQL)
sys.dm_db_missing_index_groups (Transact-SQL)
sys.dm_db_missing_index_group_stats (Transact-SQL)

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