sqlserver索引优化

/* avg_total_user_cost:减少的用户查询的平均成本 avg_user_impact:户查询可能获得的平均百分比收益 user_scans:扫描次数 user_seeks:查找次数。 equality_columns: 哪个字段缺失了索引(where 后面的筛选字段) included_columns:查询的涵盖列（简单来讲就是 select 后面的字段）。 */ SELECT  avg_user_impact,         avg_total_user_cost,          avg_total_user_cost * avg_user_impact * ( user_scans + user_seeks ) AS PossibleImprovement ,           last_user_seek ,           last_user_scan ,           [statement] AS [Object] ,           'CREATE INDEX [IDX_' + CONVERT(VARCHAR(32), GS.group_handle) + '_'           + CONVERT(VARCHAR(32), D.index_handle) + '_'           + REPLACE(REPLACE(REPLACE([STATEMENT], ']', ''), '[', ''), '.', '')           + ']' + ' ON ' + [statement] + ' (' + ISNULL(equality_columns, '')           + CASE WHEN equality_columns IS NOT NULL                       AND inequality_columns IS NOT NULL THEN ','                  ELSE ''             END + ISNULL(inequality_columns, '') + ')' + ISNULL(' INCLUDE ('                                                                 + included_columns                                                                 + ')', '') AS Create_Index_Syntax   FROM    sys.dm_db_missing_index_groups AS G           INNER JOIN sys.dm_db_missing_index_group_stats AS GS ON G.index_group_handle = GS.group_handle           INNER JOIN sys.dm_db_missing_index_details AS D ON G.index_handle = D.index_handle   ORDER BY PossibleImprovement DESC