SQL 查询表index的性能问题
- 查詢可刪除無效的index：
PRINT ‘-- Find out useless Indexes --’
select i.name, object_name(s.object_id) tblname,s.database_id,s.object_id,s.index_id,s.user_seeks,s.user_scans,s.user_lookups,s.user_updates
from sys.dm_db_index_usage_stats s
inner join sys.indexes i
on i.object_id = s.object_id and i.index_id = s.index_id
where s.database_id = db_id()
and object_name(s.object_id) not like ‘sys%’
order by s.user_updates desc - 查詢可以添加index的相關table：
PRINT ‘-- Find out Missing Indexes --’
SELECT mig.index_group_handle, mid.index_handle,
CONVERT (decimal (28,1), migs.avg_total_user_cost * migs.avg_user_impact * (migs.user_seeks + migs.user_scans)) AS improvement_measure,
‘CREATE INDEX missing_index_’ + CONVERT (varchar, mig.index_group_handle) + ‘_’ + CONVERT (varchar, mid.index_handle)
- ’ 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]
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 CONVERT (decimal (28,1), migs.avg_total_user_cost * migs.avg_user_impact * (migs.user_seeks + migs.user_scans)) > 10
ORDER BY migs.avg_total_user_cost * migs.avg_user_impact * (migs.user_seeks + migs.user_scans) DESC
一般improvement_measure排在前20的表示是可以先優化 創建index來提高性能的，create_index_statement字段表示創建index的sql