SELECT TOP 10
   ROUND(migs.avg_total_user_cost * migs.avg_user_impact * (migs.user_seeks + migs.user_scans), 0) AS improvement_measure,
   DB_NAME(mid.database_id) AS database_name,
   OBJECT_NAME(mid.object_id) AS table_name,
   'CREATE INDEX [IX_' + OBJECT_NAME(mid.object_id) + '_'
       + REPLACE(REPLACE(REPLACE(ISNULL(mid.equality_columns, ''), ', ', '_'), '[', ''), ']', '') 
       + CASE WHEN mid.inequality_columns IS NOT NULL THEN '_' + REPLACE(REPLACE(REPLACE(mid.inequality_columns, ', ', '_'), '[', ''), ']', '') ELSE '' END 
       + '] 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.user_seeks AS seek_operations,
   migs.avg_user_impact AS improvement_percent
FROM sys.dm_db_missing_index_group_stats AS migs
INNER JOIN sys.dm_db_missing_index_groups AS mig
   ON migs.group_handle = mig.index_group_handle
INNER JOIN sys.dm_db_missing_index_details AS mid
   ON mig.index_handle = mid.index_handle
WHERE mid.database_id = DB_ID()
ORDER BY improvement_measure DESC;

SELECT TOP 5
   qs.total_logical_reads / qs.execution_count AS avg_logical_reads,
   qs.execution_count,
   SUBSTRING(st.text, (qs.statement_start_offset/2) + 1,
       ((CASE qs.statement_end_offset
           WHEN -1 THEN DATALENGTH(st.text)
           ELSE qs.statement_end_offset
       END - qs.statement_start_offset)/2) + 1) AS query_text,
   qp.query_plan
FROM sys.dm_exec_query_stats AS qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) AS st
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) AS qp
WHERE qp.query_plan.exist('//RelOp[@PhysicalOp="Index Scan" or @PhysicalOp="Clustered Index Scan"]') = 1
ORDER BY avg_logical_reads DESC;

SELECT TOP 10
   t.name AS TableName,
   c.name AS ColumnName,
   SUM(us.user_scans) AS total_scans
FROM sys.tables t
JOIN sys.columns c ON t.object_id = c.object_id
LEFT JOIN sys.index_columns ic 
   ON ic.object_id = t.object_id AND ic.column_id = c.column_id
LEFT JOIN sys.indexes i ON i.object_id = t.object_id AND i.index_id = ic.index_id
LEFT JOIN sys.dm_db_index_usage_stats us ON us.object_id = t.object_id AND us.index_id = i.index_id
WHERE i.index_id IS NULL  -- 无索引列
   AND us.user_scans > 0
GROUP BY t.name, c.name
ORDER BY total_scans DESC;

-- 标准结构
CREATE INDEX IX_Table_KeyColumns
ON dbo.Table (Column1 ASC, Column2 DESC)
INCLUDE (Column3, Column4)
WITH (FILLFACTOR = 90); -- 针对频繁更新表
-- 筛选索引（针对热点数据）
CREATE INDEX IX_Orders_Active
ON dbo.Orders (OrderDate)
WHERE Status = 'Processing';

SELECT 
   OBJECT_NAME(ix.object_id) AS TableName,
   ix.name AS IndexName,
   ix.type_desc AS IndexType,
   us.user_seeks,
   us.user_scans,
   us.user_lookups,
   us.user_updates
FROM sys.dm_db_index_usage_stats us
JOIN sys.indexes ix ON us.object_id = ix.object_id AND us.index_id = ix.index_id
WHERE us.database_id = DB_ID()
   AND OBJECTPROPERTY(us.object_id, 'IsUserTable') = 1;

SELECT 
   q.query_id,
   t.query_sql_text,
   rs.avg_duration,
   rs.avg_logical_io_reads,
   p.query_plan
FROM sys.query_store_query q
JOIN sys.query_store_query_text t ON q.query_text_id = t.query_text_id
JOIN sys.query_store_plan p ON q.query_id = p.query_id
JOIN sys.query_store_runtime_stats rs ON p.plan_id = rs.plan_id
WHERE rs.last_execution_time > DATEADD(DAY, -7, GETDATE())
ORDER BY rs.avg_logical_io_reads DESC;