Work Around Divide By Zero Error in SQL SELECT - sql-server

Question

SELECT
*
FROM
RM_Sales_Union
WHERE
DOCDATE >= 'September 1, 2011'
AND DOCDATE < 'October 1, 2011'
AND CUSTNMBR = '2186020'
That query results in an error:
Msg 8134, Level 16, State 1, Line 1
Divide by zero error encountered.
if run as shown.
Excluding the last line AND CUSTNMBR = '2186020' allows the query to complete.
CUSTNMBR is a char(21) field. Divide by zero has me confused.
What is the "correct" way to work around this?
RM_Sales_Union is a union query view:
SELECT ACTNUMBR_1,
ACTNUMBR_2,
ACTNUMBR_3,
ORSLSAMT,
CUSTCLAS,
CUSTNAME,
CUSTNMBR,
SLPRSNID,
DOCABREV,
CSPORNBR,
CURNCYID,
DOCDATE,
DOCNUMBR,
GLPOSTDT,
SLSAMNT,
VOIDSTTS,
SLPRSNFN,
SPRSNSLN,
DocOrigin,
ORFRTAMT,
FRTAMNT,
COMPRCNT,
TRDISAMT,
ORTDISAM,
ORMISCAMT,
ORTAXAMT,
ORCTRXAM
FROM dbo.RM_Sales_Hist
UNION
SELECT ACTNUMBR_1,
ACTNUMBR_2,
ACTNUMBR_3,
ORSLSAMT,
CUSTCLAS,
CUSTNAME,
CUSTNMBR,
SLPRSNID,
DOCABREV,
CSPORNBR,
CURNCYID,
DOCDATE,
DOCNUMBR,
GLPOSTDT,
SLSAMNT,
VOIDSTTS,
SLPRSNFN,
SPRSNSLN,
DocOrigin,
ORFRTAMT,
FRTAMNT,
COMPRCNT,
TRDISAMT,
ORTDISAM,
ORMISCAMT,
ORTAXAMT,
ORCTRXAM
FROM dbo.RM_Sales_Open
RM_Sales_Hist and RM_Sales_Open are views defined as follows:
--RM_Sales_Hist
SELECT dbo.GL_Sales_Accounts.ACTNUMBR_1,
dbo.GL_Sales_Accounts.ACTNUMBR_2,
dbo.GL_Sales_Accounts.ACTNUMBR_3,
ISNULL(dbo.MC020102.ORSLSAMT, dbo.RM30101.SLSAMNT) AS ORSLSAMT,
dbo.RM00101.CUSTCLAS,
dbo.RM00101.CUSTNAME,
dbo.RM00101.CUSTNMBR,
dbo.RM00101.SLPRSNID,
dbo.RM40401.DOCABREV,
dbo.RM30101.CSPORNBR,
dbo.RM30101.CURNCYID,
dbo.RM30101.DOCDATE,
dbo.RM30101.DOCNUMBR,
dbo.RM30101.GLPOSTDT,
dbo.RM30101.SLSAMNT,
dbo.RM30101.VOIDSTTS,
dbo.RM00301.SLPRSNFN,
dbo.RM00301.SPRSNSLN,
'HIST' AS DocOrigin,
ISNULL(dbo.MC020102.ORFRTAMT, dbo.RM30101.FRTAMNT) AS ORFRTAMT,
dbo.RM30101.FRTAMNT,
dbo.RM00301.COMPRCNT,
dbo.RM30101.TRDISAMT,
ISNULL(dbo.MC020102.ORTDISAM, 0) AS ORTDISAM,
ISNULL(dbo.MC020102.ORMISCAMT, 0) AS ORMISCAMT,
ISNULL(dbo.MC020102.ORTAXAMT, 0) AS ORTAXAMT,
ISNULL(dbo.MC020102.ORCTRXAM, 0) AS ORCTRXAM,
dbo.RM00101.STATE
FROM dbo.GL_Sales_Accounts
INNER JOIN dbo.RM30301
ON dbo.GL_Sales_Accounts.DSTINDX = dbo.RM30301.DSTINDX
INNER JOIN dbo.RM30101
ON dbo.RM30301.CUSTNMBR = dbo.RM30101.CUSTNMBR
AND dbo.RM30301.DOCNUMBR = dbo.RM30101.DOCNUMBR
INNER JOIN dbo.RM00101
ON dbo.RM30101.CUSTNMBR = dbo.RM00101.CUSTNMBR
INNER JOIN dbo.RM40401
ON dbo.RM30101.RMDTYPAL = dbo.RM40401.RMDTYPAL
INNER JOIN dbo.RM00301
ON dbo.RM00101.SLPRSNID = dbo.RM00301.SLPRSNID
LEFT OUTER JOIN dbo.MC020102
ON dbo.RM30301.DOCNUMBR = dbo.MC020102.DOCNUMBR
WHERE ( CAST(dbo.RM30301.DOCNUMBR AS VARCHAR(21)) NOT IN (SELECT
CAST(
DOCNUMBR AS
VARCHAR(21)) AS
Expr1
FROM
dbo.Invoices_With_Display_Discounts) )
--RM_Sales_Open
SELECT dbo.GL_Sales_Accounts.ACTNUMBR_1,
dbo.GL_Sales_Accounts.ACTNUMBR_2,
dbo.GL_Sales_Accounts.ACTNUMBR_3,
ISNULL(dbo.MC020102.ORSLSAMT, 0) AS ORSLSAMT,
dbo.RM00101.CUSTCLAS,
dbo.RM00101.CUSTNAME,
dbo.RM00101.CUSTNMBR,
dbo.RM00101.SLPRSNID,
dbo.RM40401.DOCABREV,
dbo.RM20101.CSPORNBR,
dbo.RM20101.CURNCYID,
dbo.RM20101.DOCDATE,
dbo.RM20101.DOCNUMBR,
dbo.RM20101.GLPOSTDT,
dbo.RM20101.SLSAMNT,
dbo.RM20101.VOIDSTTS,
dbo.RM00301.SLPRSNFN,
dbo.RM00301.SPRSNSLN,
'OPEN' AS DocOrigin,
ISNULL(dbo.MC020102.ORFRTAMT, 0) AS ORFRTAMT,
dbo.RM20101.FRTAMNT,
dbo.RM00301.COMPRCNT,
dbo.RM20101.TRDISAMT,
ISNULL(dbo.MC020102.ORTDISAM, 0) AS ORTDISAM,
ISNULL(dbo.MC020102.ORMISCAMT, 0) AS ORMISCAMT,
ISNULL(dbo.MC020102.ORTAXAMT, 0) AS ORTAXAMT,
ISNULL(dbo.MC020102.ORCTRXAM, 0) AS ORCTRXAM,
dbo.RM00101.STATE
FROM dbo.GL_Sales_Accounts
INNER JOIN dbo.RM10101
ON dbo.GL_Sales_Accounts.DSTINDX = dbo.RM10101.DSTINDX
INNER JOIN dbo.RM20101
ON dbo.RM10101.CUSTNMBR = dbo.RM20101.CUSTNMBR
AND dbo.RM10101.DOCNUMBR = dbo.RM20101.DOCNUMBR
INNER JOIN dbo.RM00101
ON dbo.RM20101.CUSTNMBR = dbo.RM00101.CUSTNMBR
INNER JOIN dbo.RM40401
ON dbo.RM20101.RMDTYPAL = dbo.RM40401.RMDTYPAL
INNER JOIN dbo.RM00301
ON dbo.RM00101.SLPRSNID = dbo.RM00301.SLPRSNID
LEFT OUTER JOIN dbo.MC020102
ON dbo.RM10101.DOCNUMBR = dbo.MC020102.DOCNUMBR
WHERE ( CAST(dbo.RM20101.DOCNUMBR AS VARCHAR(21)) NOT IN (SELECT
CAST(
DOCNUMBR AS
varchar(21)) AS
Expr1
FROM
dbo.Invoices_With_Display_Discounts) )

Answer 1

I guess that RM_Sales_Union is a view that contains a division. The filter simply changes something like a COUNT or SUM to give zero, and it is this that is used as divisor
Change it to use something/NULLIF(..., 0) to make the expressions give NULL. Or ISNULL(something/NULLIF(..., 0), 0) to get NULL instead