Re: SQL optimization

Hi Richard

Famous IBM watchword - it depends.

In general, you want indexes (logical files with keys) that align your WHERE clause and that support your JOINs - you have a bunch, man!!

First, do you have an LF on DBWHWHS over ship date and status? That'd be my first choice, to limit the records in the main table in your JOINs.

In the JOINs, an example - have an index on the files that are joined to DBWHWHS - so do you have a logical on DBWHWHL over doc number? Stuff like that.

Indexes might not be used directly, but they can help the optimizer choose the best plan. But you need to be careful about just willy-nilly creating them. Every index means there will be more time taken for updating them when records change or are added or deleted from the table (physical file). So performance overall is a thing to look at.

I'd see what you already have - in Visual Explain, it should tell you that it chose certain indexes and maybe why - that'll help.

Here is a link to an article on SQL performance that might help - https://www.ibm.com/support/pages/sites/default/files/inline-files/$FILE/indexing and statistics 2011.pdf <https://www.ibm.com/support/pages/sites/default/files/inline-files/$FILE/indexing%20and%20statistics%202011.pdf> - by Michael Cain and Kent Milligan, true experts on this topic.

Enjoy!
Vern

On 10/13/2021 7:43 AM, Richard Reeve wrote:

This is my first shot at visual explain. It shows the creation of 4
temporary indexes. Does that indicate that I should create those 4 indexes?
All the best,

Richard Reeve


On Wed, Oct 13, 2021 at 7:38 AM Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>
wrote:

What has the optimizer suggested? Have you put this into visual explain
to see how the optimizer is actually running the statement?

Jim Oberholtzer
Agile Technology Architects

On Oct 13, 2021, at 7:11 AM, Richard Reeve <rjrjr64@xxxxxxxxx> wrote:

All,

I have this SQL statement that runs quite slow. Any idea how I might
speed this up?

SELECT

WHS.DBWHS_SHIPMENT_NBR
,WHS.DBWHS_DOC_NBR
,COR.DBCOR_ORDER_NBR
,COR.DBCOR_ORDER_TYPE
,WHL.DBWHL_DESCRIPTION
---,' ' AS sggroup
---,' ' AS sold_to-pt
,COR.DBCOR_CUST_PO_NBR
---, ' ' as fol-doc
,WHS.DBWHS_BOL_NBR
,WHS.DBWHS_WEIGHT
,WHS.DBWHS_CARTONS
,WHS.DBWHS_SHIP_DATE
,WHS.DBWHS_TRANS_ID
---,' ' as proc-id
,WHS.DBWHS_METHOD
,SHP.DBSHP_CUSTOMER
,SHP.DBSHP_NAME
,SHP.DBSHP_NAME
,SHP.DBSHP_ADDR1
,SHP.DBSHP_ADDR2
,SHP.DBSHP_CITY
,SHP.DBSHP_STATE
,SHP.DBSHP_ZIP
---,DBBLSHP.''COST CENTER
,SPC.DBSPC_COMMENT
---,'' as whn
,WDH.DBWDH_DESTINATION
,WDH.DBWDH_DEST_NAME
,SHP.DBSHP_TAX_CODE ---,' ' as tax_juris
,WDH.DBWDH_DEST_STATE
,WDH.DBWDH_DEST_CNTRY
,WDH.DBWDH_DEST_ZIP
,WHS.DBWHS_CARRIER
,VEN.DBVEN_VENDOR_VNAME---,'v' as carrier name
,WHS.DBWHS_FREIGHT_CODE---', as incoterm code
---,' ' as incoterm description
,WHS.DBWHS_FRT_CHG_CURR
,ARH.DBARH_TRAN_AMT
---,' ' as acct
,ACM.DBACM_CREDIT_LIM
---,' ' as pint
,WHS.DBWHS_COMPANY
,COR.DBCOR_ORDER_DATE
---,WDM.DBWDM_UPDATE_DATE
,WHS.DBWHS_STATUS
,WHS.DBWHS_SHIP_DATE
---,'LAW' as ERP-IDENTIFIER

FROM LAWDBF7B.DBWHWHS WHS

LEFT JOIN LAWDBF7B.DBWHWHL WHL ON WHS.DBWHS_DOC_NBR=WHL.DBWHL_DOC_NBR
LEFT JOIN LAWDBF7B.DBWHWDH WDH ON WHS.DBWHS_DOC_NBR=WDH.DBWDH_DOC_NBR
LEFT JOIN LAWDBF7B.DBBLSHP SHP ON

WHS.DBWHS_CUST_SHIP_TO=SHP.DBSHP_SHIP_TO

LEFT JOIN LAWDBF7B.DBAPVEN VEN ON WHS.DBWHS_VENDOR=VEN.DBVEN_VENDOR
LEFT JOIN LAWDBF7B.DBBLSPC SPC ON SHP.DBSHP_CUSTOMER=SPC.DBSPC_CUSTOMER
LEFT JOIN LAWDBF7B.DBARARH ARH ON ARH.DBARH_CUSTOMER=SHP.DBSHP_CUSTOMER
LEFT JOIN LAWDBF7B.DBARACM ACM ON ACM.DBACM_CUSTOMER=SHP.DBSHP_CUSTOMER
LEFT JOIN LAWDBF7B.DBBLCOR COR ON COR.DBCOR_CUSTOMER=SHP.DBSHP_CUSTOMER

WHERE WHS.DBWHS_SHIP_DATE>='20210930' AND WHS.DBWHS_STATUS='3'


All the best,

Richard Reeve
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