sys.dm_db_missing_index_columns (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns information about database table columns that are missing an index. sys.dm_db_missing_index_columns is a dynamic management function.
Syntax
sys.dm_db_missing_index_columns(index_handle)
Arguments
index_handle
An integer that uniquely identifies a missing index. It can be obtained from the following dynamic management objects:
sys.dm_db_missing_index_details (Transact-SQL)
sys.dm_db_missing_index_groups (Transact-SQL)
Table Returned
| 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. The possible values and their descriptions are: 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. |
Remarks
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 the database engine is restarted. Database administrators should periodically make backup copies of the missing index information if they want to keep it after server recycling. Use the sqlserver_start_time column in sys.dm_os_sys_info to find the last database engine startup time.
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.
Permissions
Users must be granted the VIEW SERVER STATE permission or any permission that implies the VIEW SERVER STATE permission to query this dynamic management function.
Permissions for SQL Server 2022 and later
Requires VIEW SERVER PERFORMANCE STATE permission on the server.
Examples
The following example runs a query against the Address table and then runs a query using the sys.dm_db_missing_index_columns dynamic management view to return the table columns that are missing an index.
USE AdventureWorks2022;
GO
SELECT City, StateProvinceID, PostalCode
FROM Person.Address
WHERE StateProvinceID = 9;
GO
SELECT mig.*, statement AS table_name,
column_id, column_name, column_usage
FROM sys.dm_db_missing_index_details AS mid
CROSS APPLY sys.dm_db_missing_index_columns (mid.index_handle)
INNER JOIN sys.dm_db_missing_index_groups AS mig ON mig.index_handle = mid.index_handle
ORDER BY mig.index_group_handle, mig.index_handle, column_id;
GO
Missing index suggestions should be combined when possible with one another, and with existing indexes in the current database. Learn how to apply these suggestions in tune nonclustered indexes with missing index suggestions.
Next steps
Learn more about the missing index feature in the following articles: