UPDATE_STATISTICS command is basically used when a large processing of data has occurred.
If a large number of deletions any modification or Bulk Copy into the tables has occurred, it has to update the indexes to take these changes into account. UPDATE_STATISTICS updates the indexes on these tables accordingly.
Here is T-SQL Command:
1. Update All Statistics with sp_updatestats
2. Update all statistics on a table
3. Update the statistics for an index
UPDATE STATISTICS?TableName, IndexName