# Case expressions may only be nested to level 10

They don't need to be nested at all:

` SELECT @Return = CASE WHEN LEFT(@BPartyNo, 4) = '+610' THEN SUBSTRING('0' + SUBSTRING(@BPartyNo, 5, LEN(@BPartyNo)), 11, LEN( '0' + SUBSTRING(@BPartyNo, 5, LEN(@BPartyNo)) ) ) WHEN LEFT(@BPartyNo, 3) = '+61' THEN SUBSTRING('0' + SUBSTRING(@BPartyNo, 4, LEN(@BPartyNo)), 11, LEN( '0' + SUBSTRING(@BPartyNo, 4, LEN(@BPartyNo)) ) ) WHEN LEFT(@BPartyNo, 2) = '61' THEN SUBSTRING('0' + SUBSTRING(@BPartyNo, 3, LEN(@BPartyNo)), 11, LEN( '0' + SUBSTRING(@BPartyNo, 3, LEN(@BPartyNo)) ) ) WHEN LEFT(@BPartyNo, 6) = '001161' THEN SUBSTRING('0' + SUBSTRING(@BPartyNo, 7, LEN(@BPartyNo)), 11, LEN( '0' + SUBSTRING(@BPartyNo, 7, LEN(@BPartyNo)) ) ) WHEN ( LEFT(@BPartyNo,2) = '01' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) WHEN ( LEFT(@BPartyNo,2) = '02' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) WHEN ( LEFT(@BPartyNo,2) = '03' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) WHEN ( LEFT(@BPartyNo,2) = '04' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) WHEN ( LEFT(@BPartyNo,2) = '07' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) WHEN ( LEFT(@BPartyNo,2) = '08' AND LEN(@BPartyNo) > 10 ) THEN SUBSTRING(@BPartyNo, 11, LEN(@BPartyNo)) ELSE '' END`

Personally, I would restructure your code so that you make sure the data in sanitized upon *input*, rather than trying to sanitize it now (when it's clearly too late...). Or at least do the conversion in your client language (i.e. in whatever is *calling* this sproc), which is hopefully more suited to the task of string manipulation than T-SQL is.

I had written 12 nested IIF statements for a view which errored as a Nested Case Error. I was taking 12 columns (Jan - Dec) which held numeric values. The view was to convert each month to a row. I then realized I could split the nested IIFs into two groups of six, and add them together! It worked!

`select AP.Year, AP.Period, RPA.Company, RPA.Contract, RPA.Description, RPA.PM, RPA.ProjectManager,IIF(AP.Period=1, RPA.JanNetBilled, IIF(AP.Period=2, RPA.FebNetBilled, IIF(AP.Period=3, RPA.MarNetBilled, IIF(AP.Period=4, RPA.AprNetBilled, IIF(AP.Period=5, RPA.MayNetBilled, IIF(AP.Period=6, RPA.JunNetBilled, 0)))))) +IIF(AP.Period=7, RPA.JulNetBilled, IIF(AP.Period=8, RPA.AugNetBilled, IIF(AP.Period=9, RPA.SepNetBilled, IIF(AP.Period=10, RPA.OctNetBilled, IIF(AP.Period=11, RPA.NovNetBilled, IIF(AP.Period=12, RPA.DecNetBilled, 0)))))) as BilledAmtfrom AccountPeriod APINNER JOIN REVENUE_PROJECTION_ANALYSIS RPA ON RPA.YEAR = AP.Year`