SQL Server高級進階之索引優化查詢

1.1、查找缺失索引

SELECT A.USER_SEEKS 查找次數,A.USER_SCANS 掃描次數,
    ROUND(A.AVG_TOTAL_USER_COST,2) 減少的用戶查詢的平均成本,A.AVG_USER_IMPACT 可能獲得的平均百分比收益,
    ROUND((A.USER_SEEKS+A.USER_SCANS)*A.AVG_TOTAL_USER_COST*A.AVG_USER_IMPACT/100,2) 可能的改進優勢,
    A.LAST_USER_SEEK 最近查找時間,A.LAST_USER_SCAN 最近掃描時間,C.[STATEMENT] 表名,
    'CREATE INDEX [IDX_'
        +CONVERT(VARCHAR,A.GROUP_HANDLE)+'_'+CONVERT(VARCHAR,C.INDEX_HANDLE)+'_'+REPLACE(REPLACE(REPLACE(C.[STATEMENT],']',''),'[',''),'.','')
        +']'+' ON '+C.[STATEMENT]+ ' ('
        +ISNULL(C.EQUALITY_COLUMNS,'')
        +CASE WHEN NOT C.EQUALITY_COLUMNS IS NULL AND NOT C.INEQUALITY_COLUMNS IS NULL THEN ',' ELSE '' END
        +ISNULL(C.INEQUALITY_COLUMNS,'')
        +')'
        +ISNULL(' INCLUDE ('+C.INCLUDED_COLUMNS+')','') '創建語句'
FROM sys.dm_db_missing_index_group_stats A INNER JOIN sys.dm_db_missing_index_groups B ON A.GROUP_HANDLE=B.INDEX_GROUP_HANDLE
    INNER JOIN sys.dm_db_missing_index_details C ON B.INDEX_HANDLE=C.INDEX_HANDLE
WHERE C.DATABASE_ID=DB_ID()    --默認當前數據庫，若指定數據庫則使用DB_ID(['DB_NAME'])
ORDER BY ROUND(A.USER_SEEKS*A.AVG_TOTAL_USER_COST*A.AVG_USER_IMPACT/100,2) DESC

1.2、查找未使用索引

SELECT C.NAME 表名,B.INDEX_ID 索引ID,B.NAME 索引名,
    A.USER_SEEKS 搜索次數,A.USER_SCANS 掃描次數,A.USER_LOOKUPS 查找次數,
    A.USER_UPDATES 更新次數,E.TABLEROWS 表行數,
    'DROP INDEX '+QUOTENAME(B.NAME)+' ON '+QUOTENAME(D.NAME)+'.'+QUOTENAME(OBJECT_NAME(A.OBJECT_ID)) '刪除語句'
FROM sys.dm_db_index_usage_stats A INNER JOIN sys.indexes B ON A.INDEX_ID=B.INDEX_ID AND A.OBJECT_ID=B.OBJECT_ID
    INNER JOIN sys.objects C ON A.OBJECT_ID=C.OBJECT_ID
    INNER JOIN sys.schemas D ON C.schema_id=D.schema_id
    INNER JOIN 
        (
            SELECT INDEX_ID,OBJECT_ID,SUM(ROWS) TABLEROWS
            FROM sys.partitions
            GROUP BY INDEX_ID,OBJECT_ID
        ) E ON A.INDEX_ID=E.INDEX_ID AND A.OBJECT_ID=E.OBJECT_ID
WHERE OBJECTPROPERTY(A.OBJECT_ID,'IsUserTable')=1 AND A.DATABASE_ID=DB_ID()
    AND B.TYPE_DESC='NONCLUSTERED' AND B.IS_PRIMARY_KEY=0 AND B.IS_UNIQUE_CONSTRAINT=0
    --AND C.NAME='INVMB'    --根據實際修改表名
ORDER BY (A.USER_SEEKS+A.USER_SCANS+A.USER_LOOKUPS) ASC

當更新次數很大而搜索次數及掃描次數很小或為0時，說明該索引一直在更新但基本不被使用，因而也未對查詢提供多少幫助，所以可以考慮刪除。

1.3、查看索引使用情況

SELECT OBJECT_NAME(A.[OBJECT_ID]) 表名,B.INDEX_ID 索引ID,B.[NAME] 索引名稱,B.[TYPE_DESC] 索引類型,
    A.USER_SEEKS+A.USER_SCANS+A.USER_LOOKUPS 讀,A.USER_UPDATES 寫,B.FILL_FACTOR 填充因子
FROM sys.dm_db_index_usage_stats A INNER JOIN sys.indexes B ON A.[OBJECT_ID]=B.[OBJECT_ID] AND A.INDEX_ID=B.INDEX_ID
WHERE OBJECTPROPERTY(A.[OBJECT_ID],'ISUSERTABLE')=1 
    AND A.DATABASE_ID=DB_ID()    --默認當前數據庫，若指定數據庫則使用DB_ID(['DB_NAME'])
ORDER BY OBJECT_NAME(A.[OBJECT_ID]),A.USER_UPDATES DESC,A.USER_SEEKS+A.USER_SCANS+A.USER_LOOKUPS DESC