SQL Server高级进阶之索引优化

1.1、查找缺失索引

SELECT A.USER_SEEKS 查找次数,A.USER_SCANS 扫描次数,
    ROUND(A.AVG_TOTAL_USER_COST,2) 减少的用户查询的平均成本,A.AVG_USER_IMPACT 可能获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) 可能的改进优势,
    A.LAST_USER_SEEK 最近查找时间,A.LAST_USER_SCAN 最近扫描时间,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+")","") "创建语句"
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()    --默认当前数据库，若指定数据库则使用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 搜索次数,A.USER_SCANS 扫描次数,A.USER_LOOKUPS 查找次数,
    A.USER_UPDATES 更新次数,E.TABLEROWS 表行数,
    "DROP INDEX "+QUOTENAME(B.NAME)+" ON "+QUOTENAME(D.NAME)+"."+QUOTENAME(OBJECT_NAME(A.OBJECT_ID)) "删除语句"
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"    --根据实际修改表名
ORDER BY (A.USER_SEEKS+A.USER_SCANS+A.USER_LOOKUPS) ASC

当更新次数很大而搜索次数及扫描次数很小或为0时，说明该索引一直在更新但基本不被使用，因而也未对查询提供多少帮助，所以可以考虑删除。

1.3、查看索引使用情况

SELECT OBJECT_NAME(A.[OBJECT_ID]) 表名,B.INDEX_ID 索引ID,B.[NAME] 索引名称,B.[TYPE_DESC] 索引类型,
    A.USER_SEEKS+A.USER_SCANS+A.USER_LOOKUPS 读,A.USER_UPDATES 写,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()    --默认当前数据库，若指定数据库则使用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