An SQL query with an 'IN' within the where clause is very slow to run - sql

Question

I have created an SQL query which runs but it takes about 17 seconds to complete. I have narrowed down the problem to the IN clause within the Where section of the query. This section is responsible for also finding all records within the same table where the kitref of one record matches the partofkit field of multiple other records.
Could anyone help with suggestions on how I may be able to make this more efficient?
The full SQL is below:
SELECT
tblProductions.ProductionName, tblEquipment.KitRef, tblEquipment.PartOfKit, tblEquipment.Description,
tblCollection.HireID, tblCollection.CollectedBy, Format(tblCollection.DueBack,'dd/MM/yyyy') AS DueBack, Format(tblCollection.CollectionDate,'dd/MM/yyyy') AS CollectionDate, Format(tblCollection.CollectionTime,'HH:mm') AS CollectionTime, tblCollection.DiscountPC,
tblCollectionItemized.HireLine, tblCollectionItemized.Notes, tblCollectionItemized.BookingActive, tblCollectionItemized.DepositReturned, tblTariff.Tariff
FROM tblTariff
INNER JOIN (
tblProductions INNER JOIN (
tblCollection INNER JOIN (
tblEquipment
INNER JOIN tblCollectionItemized ON tblEquipment.KitKey = tblCollectionItemized.KitKey
) ON tblCollection.HireID = tblCollectionItemized.HireID)
ON tblProductions.ProductionIDKey = tblCollection.ProductionName
) ON tblTariff.TariffKey = tblCollection.Tarriff
WHERE (
tblCollectionItemized.BookingActive='TRUE'
AND tblEquipment.PartOfKit IN (
SELECT tblEquipment.KitRef
FROM tblEquipment
INNER JOIN tblCollectionItemized ON tblEquipment.KitKey = tblCollectionItemized.KitKey
WHERE tblCollectionItemized.ReturnsNumber =43
)
)
OR (
tblCollectionItemized.BookingActive='TRUE'
AND tblCollectionItemized.ReturnsNumber =43
)

Answer 1

Not a complete answer here but using some aliases and joins in a logical order make this nightmarish query into something a lot easier to see what is going on.
SELECT
p.ProductionName
, e.KitRef
, e.PartOfKit
, e.Description
, c.HireID
, c.CollectedBy
, Format(c.DueBack,'dd/MM/yyyy') AS DueBack
, Format(c.CollectionDate,'dd/MM/yyyy') AS CollectionDate
, Format(c.CollectionTime,'HH:mm') AS CollectionTime
, c.DiscountPC
, ci.HireLine
, ci.Notes
, ci.BookingActive
, ci.DepositReturned
, t.Tariff
FROM tblTariff t
INNER JOIN tblCollection c ON t.TariffKey = c.Tarriff
INNER JOIN tblProductions p ON p.ProductionIDKey = c.ProductionName
INNER JOIN tblCollectionItemized ci ON c.HireID = ci.HireID
INNER JOIN tblEquipment e ON e.KitKey = ci.KitKey
WHERE ci.BookingActive = 'TRUE'
AND e.PartOfKit IN
(
SELECT e2.KitRef
FROM tblEquipment e2
INNER JOIN tblCollectionItemized ci2 ON e2.KitKey = ci2.KitKey
WHERE ci2.ReturnsNumber = 43
)
OR
(
ci.ReturnsNumber = 43
)

Answer 2

you can try EXISTS instead of IN and add (nolock) hint to tables
SELECT
P.ProductionName,
E.KitRef,
E.PartOfKit,
E.Description,
C.HireID,
C.CollectedBy,
Format(C.DueBack,'dd/MM/yyyy') AS DueBack,
Format(C.CollectionDate,'dd/MM/yyyy') AS CollectionDate,
Format(C.CollectionTime,'HH:mm') AS CollectionTime,
C.DiscountPC,
CI.HireLine,
CI.Notes,
CI.BookingActive,
CI.DepositReturned,
T.Tariff
FROM tblTariff T
INNER JOIN tblCollection C (nolock) ON T.TariffKey = C.Tarriff
INNER JOIN tblProductions P (nolock) ON P.ProductionIDKey = C.ProductionName
INNER JOIN tblCollectionItemized CI (nolock) ON C.HireID = CI.HireID
INNER JOIN tblEquipment E (nolock) ON E.KitKey = CI.KitKey
WHERE (
tblCollectionItemized.BookingActive='TRUE'
AND EXISTS (
SELECT *
FROM tblEquipment E2 (nolock)
INNER JOIN tblCollectionItemized CI2 (nolock) ON E2.KitKey = CI2.KitKey
WHERE CI2.ReturnsNumber =43 AND E.PartOfKit = E2.KitRef )
)
OR (
CI.BookingActive='TRUE'
AND CI.ReturnsNumber =43
)