1.查看索引的碎片率

SELECT object_name(ips.object_id) AS TableName,
    ips.index_id, name AS IndexName, avg_fragmentation_in_percent,db_name(ips.database_id) AS DatabaseName
FROM sys.dm_db_index_physical_stats
    (Db_id(DB_NAME())
        , NULL
        , NULL
        , NULL
        , NULL) AS ips
INNER JOIN sys.indexes AS SI
    ON ips.object_id = SI.object_id
    AND ips.index_id = SI.index_id
WHERE ips.avg_fragmentation_in_percent > 5 
     AND SI.index_id <> 0

索引的碎片率低于5%或者，索引的页数少于1000，可以忽略；
索引碎片率在5%-30%之间的，建议reorganize；
索引碎片率大于30%的，建议rebuild。

2.reorganize索引

alter index [索引名] on [dbo].[表名] reorganize;

3.rebuild索引

alter index [索引名] on [dbo].[表名] rebuild;

4.rebuild表上所有的索引

alter index all on [dbo].[表名] rebuild;

5.rebuild数据库中所有的索引

USE [数据库名]
GO
DECLARE @NoOfPartitions BIGINT;
DECLARE @objectid INT;
DECLARE @indexid INT;
DECLARE @idxname NVARCHAR(255);
DECLARE @objname NVARCHAR(255);
DECLARE @partitionnum BIGINT;
DECLARE @schemaname NVARCHAR(255);
DECLARE @partitions BIGINT;
DECLARE @frag FLOAT;
DECLARE @statement VARCHAR(8000);
-- checking existance of the table that we create for temporary purpose

IF OBJECT_ID('defrag_work', 'U') IS NOT NULL 
  DROP TABLE defrag_work; 


-- Copy the fragmented indexes data into defrag_work table
-- All the indexes that has fragmentation < 5 are getting stored into our work table
SELECT  [object_id] AS objectid ,
        index_id AS indexid ,
        partition_number AS partition_no ,
        avg_fragmentation_in_percent AS frag
INTO    defrag_work
FROM    sys.dm_db_index_physical_stats(DB_ID(), NULL, NULL, NULL, 'LIMITED')
WHERE   avg_fragmentation_in_percent >5.0 and index_id > 0;


-- cursor to process the list of partitions
DECLARE partitions CURSOR
FOR
    SELECT  *
    FROM    defrag_work;

-- Open the cursor.
OPEN partitions;

-- Looping through the partitions
FETCH NEXT
   FROM partitions
   INTO @objectid, @indexid, @partitionnum, @frag;

WHILE @@FETCH_STATUS = 0
    BEGIN;
        SELECT  @objname= QUOTENAME(so.name) ,
                @schemaname = QUOTENAME(ss.name)
        FROM    sys.objects AS so
                JOIN sys.schemas AS ss ON ss.schema_id = so.schema_id
        WHERE   so.object_id = @objectid;
        

        SELECT  @idxname = QUOTENAME(name)
        FROM    sys.indexes
        WHERE   object_id = @objectid
                AND index_id = @indexid;
                

        SELECT  @NoOfPartitions = COUNT(*)
        FROM    sys.partitions
        WHERE   object_id = @objectid
                AND index_id = @indexid;

/* 
Let’s say N = fragmentation percentage

N <= 5 = IGNORE
5 < N < 30 = REORGANIZE
N > 30 = REBUILD

*/
               
        IF (@frag < 30.0) -- @frag > 5 is already filtered in our first query, so we need that condition here
            BEGIN;
                SELECT  @statement = 'ALTER INDEX ' + @idxname + ' ON '
                        + @schemaname + '.' + @objname + ' REORGANIZE';
                IF @NoOfPartitions > 1
                    SELECT  @statement = @statement + ' PARTITION='
                            + CONVERT (CHAR, @partitionnum);
                EXEC (@statement);
            END;

        IF @frag >= 30.0
            BEGIN;
                SELECT  @statement = 'ALTER INDEX ' + @idxname + ' ON '
                        + @schemaname + '.' + @objname + ' REBUILD';
                IF @NoOfPartitions > 1
                    SELECT  @statement = @statement + ' PARTITION='
                            + CONVERT (CHAR, @partitionnum);
                EXEC (@statement);
            END;
        PRINT 'Executed ' + @statement;

        FETCH NEXT FROM partitions INTO @objectid, @indexid, @partitionnum,
            @frag;
    END;
-- Close and deallocate the cursor.
CLOSE partitions;
DEALLOCATE partitions;

-- drop the table
IF OBJECT_ID('defrag_work', 'U') IS NOT NULL 
  DROP TABLE defrag_work;