zoukankan      html  css  js  c++  java
  • SQL Server高级进阶之索引优化查询

    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
  • 相关阅读:
    第一次作业-准备篇
    个人作业——软件工程实践总结
    团队作业第二次—项目选题报告
    软工实践第三次作业(结对第二次作业)
    软工实践第二次作业(结对第一次作业)
    第一次作业-准备篇
    软工实践|个人作业——软件工程实践总结作业
    软工实践|团队作业第二次—项目选题报告
    软工实践|结对第二次—文献摘要热词统计及进阶需求
    软工实践|结对第一次—原型设计(文献摘要热词统计)
  • 原文地址:https://www.cnblogs.com/atomy/p/15330442.html
Copyright © 2011-2022 走看看