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What Fields Are In My Clustered Index

Last week I had to investigate a problem with a third party databases in the Health industry and was told by the product owner to look into the potential issue and provide a set of recommendations. One of my objectives were to identify tables with clustered indexes and the composition of the index.

i.e if the clustered index had multiple columns and the if the fist column was not incremental


As usual,  I hope this script helps 

IF OBJECT_ID('TEMPDB..#Temp_Constraint_Columns') IS NOT NULL
      DROP TABLE TEMPDB..#Temp_Constraint_Columns

CREATE TABLE #Temp_Constraint_Columns
      (
            IID int identity(1,1)
            ,ObejctName varchar(100)
            ,Index_Type varchar(50)
            ,PK_YN      varchar(100)
            ,Object_Type varchar(10)
            ,KeyColumns varchar(500)
      )
     
INSERT INTO #Temp_Constraint_Columns 
      (
            ObejctName
            ,Index_Type
            ,PK_YN     
            ,Object_Type     
      )
SELECT OBJECT_NAME(SI.Object_ID) ObejctName ,
            SI.Type_Desc Index_Type  ,
            CASE
                  WHEN index_id = 1 and is_primary_key = 1 THEN 'CLUSTERED_(PK-YES)'
                  WHEN index_id = 1 and is_primary_key = 0 THEN 'CLUSTERED_(PK-NO)'
                  WHEN is_primary_key = 0 THEN 'HEAP-(PK-NO)'
            END PK_YN,
            SO.TYPE Object_Type

FROM sys.indexes SI
JOIN sys.objects SO ON SI.Object_ID = SO.Object_ID
WHERE SI.index_id in (0 ,1) AND – this identifies if the index is clustered or a heap
      SO.TYPE NOT IN ('S' ,'TF')


n  This section concatinates the columns in the index

SET NOCOUNT ON
DECLARE
      @CLUSTERED_Count int ,
      @LoopCnt int ,
      @ID int ,
      @TBName varchar(100),
      @ColumnName  varchar(500)

SET @LoopCnt = 1
SET @ID = 0
SET @TBName = ''
SET @ColumnName  = ''



SELECT @CLUSTERED_Count = count(1) FROM #Temp_Constraint_Columns WHERE Index_Type = 'CLUSTERED'
-- SELECT @CLUSTERED_Count
--SET  @CLUSTERED_Count = 10


--SELECT * FROM #Temp_Constraint_Columns WHERE Index_Type = 'CLUSTERED'

WHILE @CLUSTERED_Count >= @LoopCnt
BEGIN
      SELECT  TOP 1 --IID , ObejctName 
                  @ID = IID ,
                  @TBName = ObejctName 
      FROM #Temp_Constraint_Columns WHERE Index_Type = 'CLUSTERED'  AND IID >@ID
     
                 
      -- THIS SECTION WILL IDENTIFY THE COLUMNS IN THE INDEX   
      SELECT  
                  @ColumnName   = @ColumnName   + A.COLUMN_NAME
                 
      FROM
      (                
            SELECT      TOP 100 PERCENT
                        ' ' + INC.COLUMN_NAME
                        + ' [' + INC.DATA_TYPE             
                        + ' ('+ ISNULL(CONVERT(VARCHAR(10),INC.CHARACTER_MAXIMUM_LENGTH),'') + ')]   ||'      COLUMN_NAME
            FROM    sys.indexes AS i

            INNER JOIN
                        sys.index_columns AS ic ON  i.OBJECT_ID = ic.OBJECT_ID
                                                            AND i.index_id = ic.index_id
            JOIN sys.objects SO ON I.Object_ID = SO.Object_ID 
            JOIN INFORMATION_SCHEMA.COLUMNS INC ON
                  OBJECT_NAME(ic.OBJECT_ID) = INC.TABLE_NAME AND
                  COL_NAME(ic.OBJECT_ID,ic.column_id) =     INC.COLUMN_NAME                               
            WHERE   --i.is_primary_key = 1 and
                        SO.TYPE NOT IN ('S' ,'TF') AND 
                        I.Index_ID = 1
                        and  OBJECT_NAME(ic.OBJECT_ID) = @TBName
            ORDER BY IC.key_ordinal -- PLEASE DONT REMOVE THE ORDER BY CLAUSE      
      )  A
     
           
      UPDATE #Temp_Constraint_Columns
      SET KeyColumns = SUBSTRING(@ColumnName,2,LEN(@ColumnName))
      WHERE IID = @ID
                       
     
     
       --SELECT @LoopCnt  , @ID ,  @TBName , SUBSTRING(@ColumnName,2,LEN(@ColumnName))
      SET @LoopCnt = @LoopCnt +1
      SET @ColumnName = ''
     
END


SELECT * FROM #Temp_Constraint_Columns --WHERE PK_YN = 'CLUSTERED_PK-YES'

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