Convert To Null Where Data Is Blank

Hi, where I return the address details, in some of the fields they are blank, I need these blank fields as nulls, how do i do that ?

Thanks





Code Snippet
SELECT
a.[Account Name],
a.[Line Address 1],
a.[Line Address 2],
a.[Line Address 3],
a.[Line Address 4], b.*
FROM (
SELECT
abCUSA AS Company,
abCUSB AS Account,
0 AS DeliverTo,
abcnam AS [Account Name],
abcad1 AS [Line Address 1],
abcad2 AS [Line Address 2],
abcad3 AS [Line Address 3],
abcad4 AS [Line Address 4],
CONVERT(VARCHAR(20), abCUSA) + CAST(abCUSB AS VARCHAR(20)) AS [Customer Number]
FROM
LIVEAS400.S65C422B.WRFDTA.PARNADR
) a
Inner JOIN
(
SELECT
SLDATE as Date,
SLCUSA as [Company Number],
SLCUSB as [Customer Suffix],
SLDELN as [Deliber To Number],
SLTREF as [Trans Reference],
SLCNAM as [Deliver To Name],
CONVERT(VARCHAR(20), SLCUSA) + CAST(SLCUSB AS VARCHAR(20)) AS [Customer Number],
CONVERT(VARCHAR(20), SLCUSA) + CAST(SLCUSB AS VARCHAR(20)) + CAST(SLDELN AS VARCHAR(20)) AS [Full Deliver To Number],
-- SLTRT2 as [Trans type],
CASE WHEN SLTRT2 IN (92, 93, 94, 95, 98) THEN SLGDSV * -1 ELSE SLGDSV END as [Goods Value],
CASE WHEN SLTRT2 IN (92, 93, 94, 95, 98) THEN SLVATV * -1 ELSE SLVATV END as [VAT],
CASE WHEN SLTRT2 IN (92, 93, 94, 95, 98) THEN SLTOTV * -1 ELSE SLTOTV END as Total,
SLDESC as [Trans Description]
FROM LIVEAS400.S65C422B.WRFDTA.SQLSLDGR
) b ON a.[Customer Number] = b.[Customer Number]