SQL Server 一个简单的方法检查Missing index

SQL Server 提供了一些DMV，可以帮助我们发现 Missing index, 如果下面的脚本运行后没有任何结果，说明当前数据库已经很棒了。 恭喜自己一下 :)

SELECT
  migs.avg_total_user_cost * (migs.avg_user_impact / 100.0) * (migs.user_seeks + migs.user_scans) AS

,
  'CREATE INDEX [missing_index_' + CONVERT (varchar, mig.index_group_handle) + '_' + CONVERT (varchar, mid.index_handle)
  + '_' + LEFT (PARSENAME(mid.statement, 1), 32) + ']'
  + ' ON ' + mid.statement
  + ' (' + ISNULL (mid.equality_columns,'')
    + CASE WHEN mid.equality_columns IS NOT NULL AND mid.inequality_columns IS NOT NULL THEN ',' ELSE '' END
    + ISNULL (mid.inequality_columns, '')
  + ')'
  + ISNULL (' INCLUDE (' + mid.included_columns + ')', '') AS create_index_statement,
  migs.*, mid.database_id, mid.[object_id] into #temp1
  FROM sys.dm_db_missing_index_groups mig
INNER JOIN sys.dm_db_missing_index_group_stats migs ON migs.group_handle = mig.index_group_handle
INNER JOIN sys.dm_db_missing_index_details mid ON mig.index_handle = mid.index_handle
WHERE migs.avg_total_user_cost * (migs.avg_user_impact / 100.0) * (migs.user_seeks + migs.user_scans) > 10
--and mid.statement like '%Platform%'
ORDER BY migs.avg_total_user_cost * migs.avg_user_impact * (migs.user_seeks + migs.user_scans) DESC

improvement_measure 只是一个估算的值，不是很严格的数值，它是从sys.dm_db_missing_index_group_stats中根据avg_total_user_cost, avg_user_impact, user_seeks, 还有 user_scans计算出来的，仅供参考。