SQL Server Query - Split a string into 3 parts based on 2 different common delimiters -

i'm trying build query can split combined product descriptions, colors, , sizes individual values. have table full of product descriptions, colors, , sizes. of product descriptions contain color , size each delimited specific string. of colors , sizes contained in own columns. many times, both description , color/size columns contain both color/size values. common product description combined color , size this: productdescription..-..color--.--size color delimited "..-.." , size delimited "--.--". color and/or size not exist , there no delimiter query refer to, still want split description/color or description/size, or return description , blank values color/size when neither exists...

description , size split fine, i'm having trouble color. following error:

invalid length parameter passed left or substring function. 

any appreciated!

here's have far isn't working:

select     ps.id     ,case         when ps.colorstart <= 5 , ps.sizestart <= 5 ps.description         when ps.colorstart <= 5 , ps.sizestart > 5 left(ps.description, ps.sizestart - 6)         when ps.colorstart > 5 left(ps.description, ps.colorstart - 6)         else ps.description     end descriptionwithoutcolorandsize      ,case         when ps.pcolor not null , ps.pcolor <> '' ps.pcolor         when ps.colorstart <= 5 or ps.description null or ps.description = '' ''         when ps.sizestart <= 5 , ps.colorstart > 5 substring(ps.description, ps.colorstart, 299)         when ps.sizestart > 5 , ps.colorstart > 5 substring(ps.description, ps.colorstart, ps.colorendifsizeexists - ps.colorstart + 1)             --the prior line fails         else ''     end color       ,case         when ps.psize not null , ps.psize <> '' ps.psize         when ps.sizestart <= 5 ''         else substring(ps.description, ps.sizestart, 299)     end size      (     select         p.id         ,p.description         ,p.color pcolor         ,p.size psize         ,charindex('..-..',p.description,0) + 5 colorstart         ,charindex('--.--',p.description,0) -1 colorendifsizeexists         ,len(p.description) colorendifsizedoesnotexist         ,charindex('--.--',p.description,0) + 5 sizestart              myproductstable p     ) ps 

all of problems related following case statement:

,case     when ps.pcolor not null , ps.pcolor <> '' or ps.colorendifsizeexists - ps.colorstart + 1 < 0 ps.pcolor     when ps.colorstart <=5 or ps.description null or ps.description = '' ''     when ps.sizestart <=5 , ps.colorstart > 5 substring(ps.description, ps.colorstart, 299)     when ps.sizestart > 5 , ps.colorstart > 5 substring(ps.description, ps.colorstart, ps.colorendifsizeexists - ps.colorstart + 1)      else '' end color 

i changed instances of "<=5" "<6", , added new when statment follows:

    ,case         when ps.colorendifsizeexists - ps.colorstart + 1 < 0 substring(ps.description, ps.colorstart, 299)         when ps.pcolor not null , ps.pcolor <> '' ps.pcolor         when ps.colorstart <6 or ps.description null or ps.description = '' ''         when ps.sizestart <6 , ps.colorstart > 5 substring(ps.description, ps.colorstart, 299)         when ps.sizestart > 5 , ps.colorstart > 5 substring(ps.description, ps.colorstart, ps.colorendifsizeexists - ps.colorstart + 1)         else ''     end color 

and fixed problem. don't know why... if does, please feel free explain! input.