SQL Server subquery/CTE advice

Question

I have a SQL query that runs sub 1 second:

SELECT
    GB_BR_NAME AS 'Branch',
    VM_VT_DESC AS 'VType',
    S.VM_SK_VEHICLE AS 'Vehicle',
    VM_SK_SEQUENCE AS 'Vehicle Sequence',
    CASE
        WHEN VM_VT_NU = 'N' THEN VM_SK_CONSTOTAL
        WHEN VM_VT_NU = 'U' THEN VM_SK_ADJSTOCK
    END AS 'Stock Value',
    VM_SK_CONSTOTAL AS 'Cons Total',
    VM_SK_ADJSTOCK AS 'Adj Total',
    DD_MA_DESC AS 'Manufacturer',
    DD_CL_DESCRIPTION AS 'Variant Class',
    VM_VT_NU AS 'New/Used',
    CASE
        WHEN VM_EN_PROGRESS = 'Inv' THEN 'Y'
        WHEN VM_EN_PROGRESS = 'Con' THEN 'Y'
        ELSE 'N'
    END AS 'Sold',
    VM_SK_INTFREEDATE AS 'Interest Free Date',
    CASE
        WHEN VM_SK_INTFREEDATE <= GETDATE() AND DD_MA_DESC NOT IN ('Toyota', 'Skoda', 'Lexus', 'Honda') THEN 1
        ELSE 0
    END AS 'Interest Bearing',
    VM_SK_STATUS AS 'Status'
FROM
    VM_01_STOCK S
    LEFT OUTER JOIN GB_00_BRANC B ON S.VM_SK_BRANCH = B.GB_BR_BRANCH
    LEFT OUTER JOIN VM_01_VTYPE V ON S.VM_SK_VTYPE = V.VM_VT_VTYPE
    LEFT OUTER JOIN VM_00_VEHICLE VE ON S.VM_SK_VEHICLE = VE.VM_VE_VEHICLE
    LEFT OUTER JOIN DD_00_MANUF DDM ON VE.VM_VE_MANUFACT = DDM.DD_MA_MANUFACT
    LEFT OUTER JOIN VM_01_SORDER SO ON S.VM_SK_VEHICLE = SO.VM_SO_VEHICLE AND S.VM_SK_SEQUENCE = SO.VM_SO_SEQUENCE
    LEFT OUTER JOIN DD_00_VARCLASS CL ON VE.VM_VE_VARCLASS = CL.DD_CL_CODE
    LEFT OUTER JOIN VM_01_ENQUIRY E ON S.VM_SK_ENQUIRY = E.VM_EN_ENQUIRY

WHERE
    (VM_SK_STATUS = 'A' OR VM_SK_STATUS = 'C')

This outputs ~8000 rows.

I then have a CTE which outputs ~40 rows. This also runs sub 1 second -

WITH cte (VM_SK_VEHICLE) AS
    (SELECT VM_SK_VEHICLE
    FROM VM_01_STOCK SS LEFT OUTER JOIN VM_01_VTYPE V ON SS.VM_SK_VTYPE = V.VM_VT_VTYPE LEFT OUTER JOIN VM_00_VEHICLE VE ON SS.VM_SK_VEHICLE = VE.VM_VE_VEHICLE LEFT OUTER JOIN DD_00_VARCLASS CL ON VE.VM_VE_VARCLASS = CL.DD_CL_CODE LEFT OUTER JOIN NL_01_TRANS T ON LTRIM(RTRIM(str(VM_SK_VEHICLE))) + LTRIM(RTRIM(str(VM_SK_SEQUENCE))) = NL_TR_SUFFIX LEFT OUTER JOIN PL_01_TRANS PT ON NL_TR_DAYBOOK = PL_TX_DBNUM AND NL_TR_ITEM = PL_TX_DBITEM LEFT OUTER JOIN VM_01_VSPEC VP ON VM_SK_VEHICLE = VM_VS_VEHICLE 
    WHERE (VM_SK_STATUS = 'A' OR VM_SK_STATUS = 'C') AND VM_VT_NU = 'N' AND DD_CL_CODE IN ('CAR', 'LCV', 'HGV') AND VM_VS_DESC = 'Vehicle Price' AND VM_VS_ACTCOST <> 0.00
    GROUP BY VM_SK_VEHICLE, VM_SK_SEQUENCE, VM_SK_CONSTOTAL 
    HAVING SUM(PL_TX_BASEVAL - PL_TX_BASEPAID) < (VM_SK_CONSTOTAL/2))

When I add to my main query

CASE
    WHEN S.VM_SK_VEHICLE IN (SELECT cte.VM_SK_VEHICLE FROM cte) THEN 1
    ELSE 0
END AS 'Fully Paid',

it takes ~15 minutes to start showing results. I'm doing a LEFT JOIN to join CTE to my main query.

I've also tried this with a subquery which took ~37 minutes to start showing results.

What do I need to do to get it running at proper speeds?

Thank you .

Answer 1

The trouble seems to appear with this predicate :

LTRIM(RTRIM(STR(VM_SK_VEHICLE))) + LTRIM(RTRIM(STR(VM_SK_SEQUENCE))) = NL_TR_SUFFIX

Which is not sargable at all.

Create a computed persistent column with this expression :

ALTER TABLE ??? ADD VM_SK_VEHICLE_SEQUENCE
   AS LTRIM(RTRIM(STR(VM_SK_VEHICLE))) + LTRIM(RTRIM(STR(VM_SK_SEQUENCE))) PERSISTED

If you are in a recent version of SQL Server replace "LTRIM(RTRIM(" by "TRIM("

Also, create a new index for the joined part...