Q:

Error converting data type varchar to float

Searched and searched on SO and can't figure it out
Tried CASTING each field as FLOAT to no avail, convert didn't get me any further
How can I get the below case clause to return the value stated in the THEN section?
Error:
Msg 8114, Level 16, State 5, Line 1
Error converting data type varchar to float.
section of my SQL query that makes it error:
When cust_trendd_w_costsv.terms_code like '%[%]%' and (prod.dbo.BTYS2012.average_days_pay) - (substring(cust_trendd_w_costsv.terms_code,3,2)) <= 5 THEN prod.dbo.cust_trendd_w_costsv.terms_code

average_days_pay = float
terms_code = char
Cheers!

A:

Try to use ISNUMERIC to handle strings which can't be converted:
When cust_trendd_w_costsv.terms_code like '%[%]%' 
and (prod.dbo.BTYS2012.average_days_pay) - 

(case when isnumeric(substring(cust_trendd_w_costsv.terms_code,3,2))=1 
         then cast(substring(cust_trendd_w_costsv.terms_code,3,2) as float)
         else 0
 end)
<= 5 THEN prod.dbo.cust_trendd_w_costsv.terms_code

A:

The issue that you're having is that you're specifically searching for strings that contain a % character, and then converting them (implicitly or explicitly) to float.
But strings containing % signs can't be converted to float whilst they still have a % in them. This also produces an error:
select CONVERT(float,'12.5%')

If you're wanting to convert to float, you'll need to remove the % sign first, something like:
CONVERT(float,REPLACE(terms_code,'%',''))

will just eliminate it. I'm not sure if there are any other characters in your terms_code column that may also trip it up.
You also need to be aware that SQL Server can quite aggressively re-order operations and so may attempt the above conversion on other strings in terms_code, even those not containing %. If that's the source of your error, then you need to prevent this aggressive re-ordering. Provided there are no aggregates involved, a CASE expression can usually avoid the worst of the issues - make sure that all strings that you don't want to deal with are eliminated by earlier WHEN clauses before you attempt your conversion

